Tight combination and double packaging make the stable thick silicon/carbon anode have ultra-high capacity lithium storage.

  1 Introduction to the results

  Silicon (Si) is considered as one of the most promising anode materials for high performance lithium ion batteries (LIB). However, how to alleviate the poor intrinsic conductivity and large volume change caused by petrochemical/annealing without affecting the energy density of silicon electrode is very important for the practical application of silicon in lithium ion batteries.

  In this article, Professor Yang Hui of Huazhong University of Science and Technology published "Tight binding and dual encapsulation enabled stable thick silicon/ Carbon Anode with Ultra High Volumetric Capacity for Lithium Storage ",an integration strategy for preparing compact micron-sized Si@G/CNF@NC composites is proposed. The composites have tight bonding and double packaging structure, which can give them excellent conductivity and deformation resistance, thus contributing to the realization of excellent cycle stability and good rate performance in thick electrodes. Under the ultra-high mass load of 10.8mg cm-2, the initial area capacity of Si@G/CNF@NC electrode is as high as 16.7mAh cm-2 (volume capacity is 2197.7mA hcm-3). When used together with LiNi0.95Co0.02Mn0.03O2, the bag-type full battery shows a very competitive gravity (volume) energy density of about 459.1 Wh kg-1 (about 1235.4 Wh L-1).

  2 Graphic reading guide

  Fig. 1. Schematic diagram of manufacturing process of Si@G/CNF@NC composite material.

  Fig. 2, a-c) SEM and d, e)TEM images of Si @ g/CNF @ NC composites; F) EDS characterization of Si @ G/CNF @ NC particles, and corresponding element mapping of h)C, i)Si and G) N.

  Fig. 3: a) XRD patterns of Si @ g/CNF @ NC and Si@G@NC composites, b) Raman spectra, c) nitrogen (n) adsorption/desorption isotherms, d) TGA and e) tap density; F) Si 2p, g) C 1s, h) O 1s and i) N 1s XPS spectra of Si @ G/CNF @ NC composites.

  Fig. 4, a) CV curve of Si @ G/CNF @ NC electrode at 0.1mVs-1.

  B) the electrostatic charge-discharge curve of Si @ g/CNF @ NC electrode at 0.2 A g-1;

  C) Cyclic performance of Si @ g/CNF @ NC and Si@G@NC electrodes at 0.2Ag-1,

  D) rate performance of si @ g/CNF @ NC and Si@G@NC electrodes at 0.5Ag-1.

  E) long cycle life of si @ g/CNF @ NC and Si@G@NC electrodes.

  Fig. 5, a) Cyclic performance of Si@G/CNF@NC electrodes with low (L-Si@G/CNF@NC), medium (M-Si@G/CNF@NC) and high (H-Si@G/CNF@NC)Si content at 0.5A g-1; B) Cyclic performance of M-Si @ g/CNF @ NC and H-Si@G/CNF@NC electrodes at 1. 0A g-1; C) Initial electrostatic charge-discharge curves of load electrodes with different masses; D) Linear relationship between mass load and equal capacity; E) Cyclic performance of Si@G/CNF@NC electrodes with different mass loads (2.0, 4.0 and 5.2 mg cm-2) at 0.2 a g-1.

  Fig. 6, a) In-situ TEM cell setup; B) the deformation evolution of Si @ G/CNF @ NC particles in the first lithiation/lithiation cycle; C) radial and circumferential stress distribution caused by lithium ion insertion in the 30 sector region of bare silicon and Si@G/CNF@NC particles; D) Changes of circumferential and radial stresses on the surface of pure silicon particles and Si@G/CNF@NC silicon core with state of charge (SOC).

  Fig. 7, a) CV curves of si @ g/CNF @ NC electrode at different scanning rates of 0.1 to 1.1 mV s-1; B) Fitting relationship between peak current of cathode and anode and scanning rate; C) photos of Si @ g/CNF @ NC and Si@G@NC electrodes at 0.g); G) photos of bag-type full battery based on Si@G/CNF@NC; H) consists of Si@G/CNF@NC anode and LiNi0. 95Co0.02Mn0.03O2 cathode.

  3 summary

  To sum up, we show an integrated strategy for preparing compact micron-sized Si@G/CNF@NC composites, that is, elastic GO and mechanically flexible CNF are used as inner coating and nano-surface, respectively, and combined with the outermost poly-dopamine NC coating. Experimental characterization and chemical-mechanical simulation show that the tight combination and double packaging structure of the composite material make it have excellent conductivity and resistance to volume change caused by petrochemical/desulfurization. When paired with LiNi0.95Co0.02Mn0.03O2, it shows that Si@G/CNF@NC composite has a very broad practical application prospect in thick electrodes. Bag-type battery shows a high weight (volume) energy density of ≈ 459.1 Whkg1 (≈ 1235.4 Whl1), which shows great competitiveness in silicon-based electrodes. This study provides a simple and controllable strategy to construct high-density micron-scale composite electrode materials, which can significantly improve the volume and area capacity of electrodes and have a wide range of practical applications in rechargeable LIBs.

  Literature: https://doi.org/10.1002/smll.202303864

  Source: material analysis and application