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In this study, we present a holistic analysis of the stock and emissions of poly- and perfluoroalkyl substances (PFAS) in California carpet in 2000-2030. Our high estimate is that, in 2017, the total PFAS accumulated in in-use carpet stock and landfilled carpet are ∼60 and ∼120 tonnes, respectively, and the resultant PFAS emissions are ∼800 and ∼100 kg, respectively. Among the three subclasses (side-chain polymers, PFAA, and nonpolymeric precursors), side-chain polymers dominate the in-use stock and landfill accumulation, while nonpolymeric precursors dominate the resultant emissions. Our low estimate is typically 8-15% of the high estimate and follows similar trends and subclass breakdowns as the high estimate. California's new Carpet Stewardship Regulations (24% recycling of end-of-life carpet) will reduce the landfilled PFAS by 6% (7 tonnes) at the cost of increasing the in-use stock by 2% (2 tonnes) in 2030. Aggressive PFAS phase-out by carpet manufacturers (i.e., reduce PFAS use by 15% annually starting 2020) could reduce the in-use PFAS stock by 50% by 2030, but its impact on the total landfilled PFAS is limited. The shift toward short-chain PFAS will also significantly reduce the in-use stock of long-chain PFAS in carpet by 2030 (only 25% of the total PFAS will be long-chain). Among the data gaps identified, a key one is the current area-based PFAS emission reporting (i.e., g PFAS emitted/area carpet/time), which leads to the counterintuitive result that reducing the PFAS use in carpet production has no impact on the PFAS emissions from in-use stock and landfills. Future technical studies should either confirm this or consider a mass-based unit (e.g., g PFAS emitted/g PFAS used/time) for better integration into regional substance flow analysis. Other noticeable data gaps include the lack of time-series data on emissions from the in-use stock and on leaching of side-chain polymers from landfills.

The realization of practical nonaqueous lithium-air batteries (LABs) calls for novel strategies to address their numerous theoretical and technical challenges. LiOH formation/decomposition has recently been proposed as a promising alternative route to cycling LABs via Li

The Mn-based mixed polyanion is expected to be a promising cathode material for sodium-ion batteries applied to large-scale smart grid energy storage systems due to its stable three-dimensional crystal structure, low cost, and high energy density. Herein, a novel carbon nanotube (CNT)-modified mixed-polyanion material (Na4Mn2Co(PO4)2P2O7) with a high voltage of 3.86 V is synthesized by a facile spray-drying method. The well-designed Na4Mn2Co(PO4)2P2O7/C-CNTs microsphere has excellent electronic and ionic conductivity by virtue of the carbon nanotube conductive skeleton. The as-prepared Na4Mn2Co(PO4)2P2O7/C-CNTs composite exhibits a reversible initial discharge capacity of 96.1 mA h g-1 and an energy density of 371 Wh kg-1 at 0.1 C. Furthermore, Na4Mn2Co(PO4)2P2O7/C-CNTs and hard carbon are assembled into a full battery, which delivers an initial discharge capacity of 88.8 mA h g-1, a working voltage of 3.85 V, and a promising energy density of 249.9 Wh kg-1 at 0.1 C. Therefore, the outstanding performance makes the Na4Mn2Co(PO4)2P2O7/C-CNTs material a potential candidate for large-scale applications of sodium-ion batteries.

： Lithium-sulfur (Li-S) batteries are extremely attractive because of their high theoretical capacities, energy densities, and cost-effectiveness, as well as the environmental friendliness of elemental sulfur. However, the commercialization of Li-S batteries is impeded by fast capacity fading and harsh self-discharge. To overcome these issues, effort has been dedicated to improving performance by designing the electrode structure and composition, which is often expensive and complex. In this study, modification of the separator by a combination of commercial titanium monoxide and multiwall carbon nanotubes (TiO/MWCNTs) was first designed, which is a low-cost and simple preparation process. The cooperative effect of TiO and MWCNTs capacitates the feedback of the Li-S cell with a relatively high premier discharge capacity of 1527.2 mAh g−1, and excellent cycling stability is obtained up to 1000 cycles at 0.5 C with a negligible fading rate of 0.057% per cycle. And the self-discharge behavior was improved obviously. When the time of rest was extended to 96 h, the capacity attenuation of the cell with the TiO/MWCNT coating was only 12.4%. The use of a TiO/MWCNT-coated separator is a feasible method for the commercial success of high-performance Li-S batteries.

Potassium-doped Na3V2(PO4)2F3@CNT(NVPF@CNT) is employed as a promising cathode for sodium-ion batteries via a simple sol-gel method in order to improve the intrinsic electronic conductivity and ion diffusion rate. The effects of K substitution on the crystal structure and electrochemical performance of NVPF are discussed. It is found that by introducing a moderate amount of K to replace the Na sites in the NVPF crystal structure, the ion diffusion path is effectively broadened, so the electrochemical performance is greatly improved. Excellent cyclic performance with a high specific capacity of 120 mAh g−1 is achieved at a low rate of 1C. After 1600 cycles at a discharge rate of 10C, the discharge capacity can still achieve values higher than 90 mAh g−1. Even at a high rate of 50C, the capacity retention ofNKVPF@CNTcould still remain as high as 90% after nearly 6000 cycles. In order to obtain a better understanding of the relationship between the ion doping and kinetic properties, a Rietveld refinement analysis and Randles-Sevcik equation-based theory are proposed in this research. This is the first time that potassium ion substitution has been used to improve the performance of NVPF and is proved to be an effective way to modify the lattice structure. Such work aids in the progression of sodium-based batteries.

Na2+2xFe2-x (SO4)3 is considered a promising cathode material for advanced sodium ion batteries with higher energy density due to its advantage of high-voltage, earth-abundant elements material and low-cost. However, strongly impeded by its fatal environmental sensitivity and low electronic conductivity, the NFS usually shows unsatisfactory electrochemical performance. Herein, a facile synthesis of microspherical NFS@reduced graphene oxide composites are synthesized through spray-drying method. The well-designed microspherical NFS@rGO with confined NFS nanocrystal in the three-dimensional graphene framework exhibits superb electronic and ionic conductivity as well as structural stability. The NFS@rGO composites show outstanding electrochemical properties: high sodium storage capacity (99 mAh g−1 at 0.1 C), superior rate performance (78 mAh g−1 at 60 C and even up to 72 mAh g−1 at 80 C), ultralong cycling stability (80.8% capacity retention after 2000 cycles at 30 C). The excellent performance makes the NFS@rGO material a prospective electrode candidate for large-scale SIBs.

The low energy density and the unsatisfactory cycling stability of cathode materials in sodium-ion battery systems have restricted their wider application. Here, a representative high voltage cathode of Na4Co3(PO4)2P2O7 (NCPP) was modified through Al doping. The as-prepared Na3.85Co2.85Al0.15(PO4)2P2O7 (Al0.15-NCPP) can deliver a discharge capacity of 99.5 mA h g−1 at 0.5C. A superior rate capability (80.3 mA h g−1 at 20C and 73.4 mA h g−1 at 50C) as well as excellent ultralong cycling stability (96.3% capacity retention after 900 cycles at 10C and 82.7% capacity retention after 8000 cycles at 30C) can be obtained. The excellent sodium storage properties are benefited from the advantages of Al doping. Al doping not only enhances ionic conductivity, but also improves the structural stability. Al0.15-NCPP, which has outstanding electrochemical properties, has been proposed as a very attractive high voltage cathode material for sodium-ion batteries. More impressively, a full cell assembled with an Al0.15-NCPP cathode and hard carbon (HC) anode exhibits distinguished rate/cycling performances (70.6 mA h g−1 at 30C and 95% capacity retention after 200 cycles at 1C) and an extremely high output voltage of 4.36 V, thus providing a preview of its practical application. In addition, our research can be used to enhance the electrochemical properties of other polyanion-based high voltage electrode materials.

Polyethylene terephthalate (PET) used to account for ≈50% of China’s waste plastics import. In 2018, the Chinese government banned the import of waste plastics due to the environmental and health burdens caused by the waste treatment processes. However, the recycling of waste PET also helps avoid the production of virgin PET and several corresponding environmental impacts such as fossil resources use and carbon emission, which remain unquantified. We combine material flow analysis and life cycle assessment to map the PET bottle cycles and evaluate the relevant environmental performances during 2000–2018 in China. The cumulative recycling of PET bottles amounted to 78 million tons (Mt) in China during the studied period. Among them, 29 Mt waste PET bottles (37% of total recycling) were imported from abroad and accounted for 40% of the world’s total export. Most waste PET bottles in China was recycled to produce PET fibers, which significantly improved global PET circularity, reduced the use of virgin PET material, and saved about 109 Mt oil-eq of fossil resources (e.g., coal and oil) use and avoided 233 Mt CO2-eq emissions. Despite these benefits, the environmental burdens with regional impacts during waste plastics treatment should be significantly reduced, and technologies for close-loop, namely bottle-to-bottle, recycling of PET should be further developed and widely applied. 72 Mt waste PET bottles (37% were imported abroad) were recycled in China, which promoted global plastic circularity and sustainability.

Bisphenol A (BPA), a synthetic organic chemical, is creating a new category of ecological and human health challenges due to unintended leakage. Effectively managing the use and leakage of BPA can benefit from an understanding of the anthropogenic BPA cycles (i.e., the size of BPA flows and stocks). In this work, we provide a dynamic analysis of the anthropogenic BPA cycles in China for 2000-2014. We find that China's BPA consumption has increased 10-fold since 2000, to ∼3 million tonnes/year. With the increasing consumption, China's in-use BPA stock has increased 500-fold to 14.0 million tonnes (i.e., 10.2 kg BPA/capita). It is unclear whether a saturation point has been reached, but in 2004-2014, China's in-use BPA stock has been increasing by 0.8 kg BPA/capita annually. Electronic products are the biggest contributor, responsible for roughly one-third of China's in-use BPA stock. Optical media (DVD/VCD/CDs) is the largest contributor to China's current End-of-Life (EoL) BPA flow, totaling 0.9 million tonnes/year. However, the EoL BPA flow due to e-waste will increase quickly, and will soon become the largest EoL BPA flow. The changing quantities and sources of EoL BPA flows may require a shift in the macroscopic BPA management strategies.

Na4Fe3(PO4)2P2O7 is considered to be a practical cathode material due to the wide source and low price of raw materials. However, the inherent isolation properties of the PO43− group result in low electronic conductivity and, subsequently, a low discharge capacity and poor cycling stability. Herein, polyvinylpyrrolidone assisted electrospinning method is used to synthesize Na4Fe3(PO4)2P2O7 nanoparticles embedded in carbon nanoribbons. The network structure of active materials wrapped in crosslinked carbon nanoribbons not only enables the ultra-fast transfer of electrons on the three-dimensional “highway” between the nanoparticles but also inhibits the aggregation of nanoparticles. These nanoribbons exhibit remarkable electrochemical performance, resulting from their exceptional electronic and ionic conductivity: high capacity of 128.6 mAh g−1 at 0.1C (1 C = 128.9 mAh g−1), extra-high rate capability (61.2 mAh g−1 at 50 C), and ultra-long cycle (72% capacity retention after 5000 cycles at 50 C). Meanwhile, Na4Fe3(PO4)2P2O7 nanoribbon also shows excellent low temperature properties. At −15 °C, the nanoribbon delivers 84.5 mAh g−1 of discharge capacity at 0.05C and displays long-term cycle performance (80.8% capacity retention after 700 cycles at 0.5C). Therefore, the Na4Fe3(PO4)2P2O7 nanoribbon with excellent electrochemical performance can be considered an attractive cathode electrode for the commercialization of sodium-ion battery.

The Mn-based mixed polyanion is expected to be a promising cathode material for sodium-ion batteries applied to large-scale smart grid energy storage systems due to its stable three-dimensional crystal structure, low cost, and high energy density. Herein, a novel carbon nanotube (CNT)-modified mixed-polyanion material (Na

Tungsten is deemed a critical raw material by many nations, given its irreplaceable use in industrial and military applications. In particular, much concern has been drawn to China's high share in global tungsten supply. While various studies have focused on the criticality of tungsten, few have specifically explored how tungsten is produced, consumed, and traded. In this paper, the dynamic material flow analysis is applied to quantify China's annual tungsten cycle from 1949 – 2017. It is estimated that total tungsten mined from ores in China over the past 68-year period is ~2500 kilo-tons (kt). Among those, ~750 kt of tungsten has been exported to other countries, and around 970 kt tungsten is domestically consumed. It is noted ≈1720 kt has been lost from mining, production, and end-of-life stage, and merely ~130 kt has been recycled as end-of-life scrap. Our material flow analysis further refined China's tungsten dominance. Although China currently dominates the global production of tungsten, this dominance will not extend too far into the future given China's limited share of world tungsten reserves and its declining ore quality. Our trade flow analysis reveals that China imported ~35 kt of high value-added downstream tungsten products from outside manufacturers, whose mineral resource was originally imported from China. At present, China by itself is experiencing overcapacity issues in the primary production, which discourages the recycling of at end-of-life (EoL) stage and makes the EoL recycling rate only 10%. It is noted that the percentage of Chinese tungsten for domestic consumption has been increasing in the past few years. This highlights the need for systematic measures from stakeholders along the tungsten cycle to promote sustainable practices for efficient tungsten production, use, and recycling in China. Meanwhile, the results also suggest the importance of monitoring the criticality of tungsten and other critical minerals from a dynamic and material cycle perspective.

Stabilizing the lithium anode while inhibiting the shuttle effect to achieve stable circulation under high sulfur loading is an inevitable problem for the commercialization of lithium-sulfur batteries. A low cost of raw materials and a simple synthesis are also important prerequisites for product commercialization. In this paper, zinc sulfide (ZnS) nanoparticles embedded in nitrogen-doped 3D-carbon nanosheets (NCNS) are proposed as modified separator materials. During high-temperature carbonization of the carbon materials, a zinc sulphide phase transition occurs, resulting in an anion vacancy (S2-) and an unsaturated Zn centre. While maintaining catalytic activity, the unsaturated Zn centre in ZnS acts as a Lewis acid to form a coordinate bond with the polysulfide. Furthermore, a uniform distribution of N heteroatoms can effectively regulate Li+ flux through the separator, thereby achieving a stable cycle for the lithium anode. A cell with the ZnS/NCNS-modified separator can achieve a stable cycle at 0.5 C and superior electrochemical performance even with an areal sulfur loading of 6 mg cm−2. An excellent reduction in self-discharge was also confirmed by a 4% capacity attenuation after resting for 4 days. This work provides new insight on the design and preparation of novel separators for highly stable Li–S batteries via a “green” and cost-effective approach.

Symmetric sodium ion full batteries with high energy density are expected to become promising storage devices. Na7V4(P2O7)4(PO4)/C can be assembled into a high energy density symmetric full battery due to 3.85 V operating voltage as a cathode and 0.94 V operating voltage as an anode. Here, the as-prepared Na7V4(P2O7)4(PO4)/C-GA (graphene aerogel) displays excellent electrochemical behavior as both cathode and anode. As the cathode, it can deliver a reversible capacity of 91.4 mA h g−1 at 1C (1C = 92.8 mA h g−1) and even shows 74 mA h g−1 capacity at 100C. Meanwhile, an ultra-long cycling property is obtained (77.2% capacity retention after 5000 cycles at 20C). As the anode, it can output 92.4 mA h g−1 at 25 mA g−1 and has a 79.2% capacity retention after 300 cycles at 50 mA g−1. Interestingly, the symmetric full battery assembled with NVPP/C-GA outputs an initial 81.9 mA h g−1 capacity, a high 2.84 V working voltage, and 232.6 Wh kg−1 energy density at 25 mA g−1. Therefore, our work shows potential application prospects of the symmetric full battery with Na7V4(P2O7)4(PO4)/C-GA in energy storage systems.

MoS2 has attracted remarkable attention, attributed to its high specific capacity and graphite-like structure. However, the low rate capability and poor cycle stability are two major obstacles that hinder the practical application of MoS2 in sodium-ion batteries (SIBs). Herein, MoS2 grows vertically on the surface of reduced graphene oxide (rGO) and forms a nanowall structure by electrostatic attraction, whose growth has been induced by cetyltrimethyl ammonium bromide (CTAB). This unique nanowall has a large specific surface area, which not only exposes plenty of active sites and shortens the diffusion distance of Na+, but also improves the electronic conductivity and structural stability. Meanwhile, detailed kinetic analysis is also employed to explain the Na+ storage behavior. The pseudo capacitance-dominated contribution ensures a more stable and much faster Na+ storage. Therefore, the MoS2@rGO composite displays excellent electrochemical performance. For example, the capacity of the MoS2@rGO composite can still be maintained at 571.5 mA h g−1 with 94.1% retention, after 100 cycles at 0.1 A g−1. Impressively, MoS2@rGO still exhibits a considerable capacity of 124 mA h g−1 at an ultra-high current density of 40 A g−1. The excellent performance makes the MoS2@rGO material a prospective electrode for use in large-scale SIBs.

Rechargeable aqueous zinc-ion batteries (ZIBs) are possible future replacements for large-scale energy storage devices because of their safety, low cost, and abundance of materials. Finding a competitive cathode material suitable for zinc-ion insertion/de-insertion, needed to achieve high reversible capacity and long cycle stability, is one of the most important and arduous challenges. For the first time, nickel and cobalt co-substituted spinel ZnMn2O4 nanoparticles, homogeneously loaded onto N-doped reduced graphene oxide (ZnNixCoyMn2-x-yO4@N-rGO), were synthesised through a one-step hydrothermal method and applied as a cathode material to accommodate the intercalation of zinc ions. The as-prepared ZnNixCoyMn2-x-yO4@N-rGO displayed excellent electrochemical performance, with a reversible capacity of 95.4 mA h g−1, achieved at 1000 mA g−1 after 900 cycles, and a capacity retention ratio of 79%. When the current density increased from 10 mA g−1 to 1500 mA g−1, high capacity (200.5 mA h g−1 to 93.5 mA h g−1) was achieved, which was much higher than that of ZMO@N-rGO without nickel and cobalt co-substituting (184 mA h g−1 to 59.2 mA h g−1), demonstrating excellent rate performance. These excellent electrochemical properties are attributed to the co-substituting of nickel and cobalt elements, which is an effective approach to promote Zn2+ de-intercalation and to stabilize the spinel structure in order to suppress the Jahn-Teller distortion of Mn3+. Therefore, nickel and cobalt co-substituting of spinel ZnMn2O4@N-rGO with a stable structure opens up new possibilities for large-scale application of rechargeable, aqueous ZIBs.