Abstract
Autonomic self-healing (SH), namely, the ability to repair damages from mechanical stress spontaneously, is polarizing attention in the field of new-generation electrochemical devices. This property is highly attractive to enhance the durability of rechargeable Li-ion batteries (LIBs) or Na-ion batteries (SIBs), where high-performing anode active materials (silicon, phosphorus, etc.) are strongly affected by volume expansion and phase changes upon ion insertion. Here, we applied a SH strategy, based on the dynamic quadruple hydrogen bonding, to nanosized black phosphorus (BP) anodes for Na-ion cells. The goal is to overcome drastic capacity decay and short lifetime, resulting from mechanical damages induced by the volumetric expansion/contraction upon sodiation/desodiation. Specifically, we developed novel ureidopyrimidinone (UPy)-telechelic systems and related blends with poly(ethylene oxide) as novel and green binders alternative to the more conventional ones, such as polyacrylic acid and carboxymethylcellulose, which are typically used in SIBs. BP anodes show impressively improved (more than 6 times) capacity retention when employing the new SH polymeric blend. In particular, the SH electrode still works at a current density higher than 3.5 A g–1, whereas the standard BP electrode exhibits very poor performances already at current densities lower than 0.5 A g–1. This is the result of better adhesion, buffering properties, and spontaneous damage reparation.
Highlights
The future next-generation metal (M)-ion batteries [M = Li-ion batteries (LIBs) and Na-ion batteries (SIBs)] need to be improved in terms of enhanced durability, lower cost per stored energy, and sustainability
Di-(OH)-terminated poly(ethylene glycol) (PEG) were purchased with different molecular weights (PEGn, MW = 4000 Da, n = 91; MW = 6000 Da, n = 136; MW = 10,000 Da, n = 227; and MW = 35,000 Da, n = 795) as monodisperse products from different commercial sources and were used as received
Differential scanning calorimetry (DSC) analyses were performed with a Q2000 instrument (TA Instruments, USA) by heating the samples from −80 to 150 °C at 5 °C/min under a N2 atmosphere in Al crucibles sealed in the glove box. 1H and 13C NMR high-resolution spectra were recorded on Bruker
Summary
Some of the most crucial issues which are detrimental on the battery performances are related to the physical chemistry of the electroactive materials selected as anode components.[1] The electrochemical processes taking place in the anode compartment, involve dimensional/ structural evolutions which cause degeneration, damage, and serious cycling failure. This is particular evident in anodes based on silicon[2] or phosphorus,[3] which normally undergo huge volumetric expansion/contraction upon full Li or Na insertion/ deinsertion, thereby forcing large material strains. All the previously reported Si- and P-based anodes showed capacity fading higher than 70−80% over the first [10−20] cycles.[2,3]
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