Increasing the energy density of conventional lithium-ion batteries (LIBs) is important for satisfying the demands of electric vehicles and advanced electronics.Silicon is considered as one of the most-promising anodes to replace the traditional graphite anode for the realization of high-energy LIBs due to its extremely high theoretical capacity, although its severe volume changes during lithiation/delithiation have led to a big challenge for practical application. In contrast, the co-utilization of Si and graphite has been well recognized as one of the preferred strategies for commercialization in the near future. In this review, we focus on different carbonaceous additives, such as carbon nanotubes, reduced graphene oxide, and pyrolyzed carbon derived from precursors such as pitch, sugars, heteroatom polymers, and so forth, which play an important role in constructing micrometersized hierarchical structures of silicon/graphite/carbon (Si/G/C) composites and tailoring the morphology and surface with good structural stability, good adhesion, high electrical conductivity, high tap density, and good interface chemistry to achieve high capacity and long cycling stability simultaneously. We first discuss the importance and challenge of the co-utilization of Si and graphite. Then, we carefully review and compare the improved effects of various types of carbonaceous materials and their associated structures on the electrochemical performance of Si/G/C composites. We also review the diverse synthesis techniques and treatment methods, which are also significant factors for optimizing Si/G/C composites. Finally, we provide a pertinent evaluation of these forms of carbon according to their suitability for commercialization. We also make far-ranging suggestions with regard to the selection of proper carbonaceous materials and the design of Si/G/C composites for further development. K E Y W O R D Scarbonaceous additives, graphite, high energy, lithium-ion batteries, silicon ---

Light propagation in optical lattices of driven cold atoms exhibits non-Hermitian degeneracies when the first-order modulation amplitudes of real and imaginary parts of the probe susceptibility are manipulated to be balanced. At these degeneracies, one may observe complete unidirectional reflectionless light propagation. This strictly occurs with no gain and can be easily tuned and fully reversed as supported by the transfer-matrix calculations and explained via a coupled-mode analysis. DOI: 10.1103/PhysRevLett.113.123004 PACS numbers: 37.10.Jk, 11.30.Er, 42.25.Bs, 42.50.Gy Much attention has been devoted to the development of artificial metamaterials for achieving optical functionalities not available in nature. Photonic crystals [1] and lefthanded materials [2] are prominent instances tailored to stretch the rules of light propagation and interaction. Such metamaterials have seeded new paradigms in optical, optoelectronic, and optomechanical devices [3][4][5][6]. Nevertheless, some tasks are more difficult than others with unidirectional light transport being a most pronounced example. Significant progress has been made in recent years by developing optical materials with parity-time (PT) symmetry to attain unidirectional light invisibility [7][8][9][10][11][12][13][14][15][16]. PT-symmetric metamaterials require a delicate balance of gain and loss whereby the complex refraction index satisfies nðzÞ ¼ n à ð−zÞ and are typically made of periodic solid microstructures. Homogeneous atomic vapors driven into three-level [17,18] or four-level [19] configurations have also been proposed to realize PT-symmetric optical potentials via rather complicated spatial modulations of two driving fields. Such proposals have obvious advantages of real-time all-optical reconfigurable capabilities and implicit disadvantages of intractable field modulations and considerable symmetry errors. Large optical nonreciprocities may also be achieved by exploiting the asymmetric Doppler shift in moving atomic Bragg mirrors [20], and proofof-principle experiments have been carried out [21].The great interest in PT-symmetric complex media stemmed, however, from the non-Hermitian extensions of quantum mechanics and quantum field theories [22,23], and it is perhaps worth going back to the essential nonHermitian behavior of light transport to get a broader picture on reciprocity violations and unidirectional reflectionlessness. Take, e.g., a typical one-dimensional (1D) light scattering process as shown in Fig. 1(a) where the outgoing field amplitudes fE − L ; E þ R g are related to the incoming field amplitudes fE − R ; E þ L g by a scattering matrix S [24], the eigenvectors of which are defined byThe complex amplitudes t, r L , and r R of the (S) matrix in Eq.(1) denote, as usual, the reciprocal transmission and the reflection for incidence from the left and from the right. In general, the matrix S is non-Hermitian, its eigenvalues λ AE s ¼ t AE ffiffiffiffiffiffiffiffiffi ffi r L r R p are complex, and its eigenvectors ðAE ffiffiffiffiff...

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Using p-phenylenediamine as a precursor, p-carbon dots (p-CDs) with strong red-light emission were encapsulated into a metal-organic framework (MOF) followed by introduction of green light-emitting Tb to form a two-color light-emitting hybrid (Tb@p-CDs/MOF). The as-prepared fluorescent-functionalized MOF not only maintained the excellent optical properties of p-CDs and Tb to give strong emission, but also had good chemical and physical properties. The chosen p-CDs were aggregated readily in water, which led to only very weak photoluminescence, whereas the opposite effect was noted in the organic solvents ethanol, dimethylformamide and cyclopropane. Therefore, the as-prepared hybrid showed different color light emission in water or organic solvents, and acted as a ratiometric and colorimetric fluorescent probe to detect water content in organic solvents. Moreover, this hybrid also served as a ratiometric luminescent sensor for detection of relative humidity (RH): the ratio of light intensity at 545 nm to that at 605 nm increased linearly with increasing RH from 33.0% to 85.1% in the atmosphere.

Sulfides are promising anode candidates because of their relatively large theoretical discharge/charge specific capacity and pretty small volume changes, but suffers from sluggish kinetics and structural instability upon cycling. Phase engineering can be designed to overcome the weakness of the electrochemical performance of sulfide anodes. By choosing nickel sulfides (α‐NiS, β‐NiS, and NiS2) supported by reduced graphene oxide (rGO) as model systems, it is demonstrated that the nickel sulfides with different crystal structures show different performances in both sodium‐ion and potassium‐ion batteries. In particular, the α‐NiS/rGO display superior stable capacity (≈426 mAh g−1 for 500 cycles at 500 mA g−1) and exceptional rate capability (315 mAh g−1 at 2000 mA g−1). The combined density functional theory calculations and experimental studies reveal that the hexagonal structure is more conducive to ion absorption and conduction, a higher pseudocapacitive contribution, and higher mechanical ability to relieve the stress caused by the volume changes. Correspondingly, the phase engineered nickel sulfide coupled with the conducting rGO network synergistically boosts the electrochemical performance of batteries. This work sheds light on the use of phase engineering as an essential strategy for exploring materials with satisfactory electrochemical performance for sodium‐ion and potassium‐ion batteries.