Electroactive organics have attracted significant attention as electrode materials for next-generation rechargeable batteries because of their structural diversity, molecular adjustability, abundance, flexibility, environmental friendliness and low cost. To date, a large number of organic materials have been applied in a variety of energy storage devices. However, the inherent problems of organic materials, such as their dissolution in electrolytes and low electronic conductivity, have restricted the development of organic electrodes. In order to solve these problems, many groups have carried out research and remarkable progress has been made. Nevertheless, most reviews of organic electrodes have focused on the positive electrode rather than the negative electrode. This review first provides an overview of the recent work on organic anodes for Li- and Na-ion batteries. Six categories of organic anodes are summarized and discussed. Many of the key factors that influence the electrochemical performance of organic anodes are highlighted and their prospects and remaining challenges are evaluated.
The development of Si-based lithium-ion batteries is restricted by the large volume expansion of Si materials and the unstable solid electrolyte interface film. Herein, a novel Si capsule with in situ developed polymethyl methacrylate (PMMA) shell is prepared via microemulsion polymerization, in which PMMA has high lithium conductivity, high elasticity, certain viscosity in electrolytes, as well as good electrolyte retention ability. Taking advantage of the microcapsule structure with the PMMA capsid, the novel Si capsule anode retains 1.2 mA h/cm 2 at a current density of 2 A/g after 200 electrochemical cycles and delivers higher than 66% of its initial capacity at 42 A/g.
Silicon
(Si) is deemed to be the next-generation lithium-ion battery
anode. However, on account of the poor electronic conductivity of
Si materials and the instability of the solid electrolyte interphase
layer, the electrochemical performance of Si anodes is far from reaching
the application level. In this work, a multifunctional poly(propargylamine)
(PPA) interlayer is constructed on the Si surface via a simple in situ polymerization method. Benefiting from the electronic
conductivity, ionic conductivity, robust interphase interactions for
hydrogen bonding, and stability of multifunctional PPA, the optimized
Si@PPA-7% electrode shows improved lithium storage capability. A high
capacity of 1316.3 mAh g–1 is retained after 500
cycles at 2.1 A g–1, and 2370.3 mAh g–1 can be delivered at 42 A g–1, which are in stark
contrast to the unmodified Si electrode. Furthermore, the rate and
cycle capabilities of the LiFePO4//Si@PPA-7% full cell
are also obviously better than those of LiFePO4//Si.
Silicon (Si)-based batteries can only work in a narrow
temperature
range, where their subzero operation has been severely hampered by
the sluggish charge transfer and ion diffusion processes. In overcoming
such kinetic barriers, a weakly solvating electrolyte is tailored
herein, which bypasses the Li+ desolvation difficulties
by its fluorinated structure that lowers the Li+ solvating
capability. Specifically, our recipe is based on 1 M LiFSI in fluoroethylene
carbonate (FEC)/bis(2,2,2-trifluoroethyl) carbonate (BTFC) solvents.
Additional incorporation of poor-solvating ethyl trifluoroacetate
(ETFA) cosolvent further weakens the electrolyte solvation power,
while efficaciously lowering the electrolyte viscosity and melting
point. Such a combination affords prolonged Si cyclability for 200
cycles at RT (capacity-decay rate of 0.0945% per cycle). Even at −20
°C, the Si electrode still delivers a discharge capacity as high
as 2005.7 mAh g–1 that proceeds for 200 cycles.
Pairing with a commercial LiNi0.5Co0.2Mn0.3O2 cathode, the full cell affords a capacity
of 104.6 mAh g–1 when being charged/discharged at
−20 °C, which presented quite stable performance over
100 cycles.
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