Perspectives in Electrochemical in situ Structural Reconstruction of Cathode Materials for Multivalent-ion Storage

Multivalent-ion(such as Zn^(2+),Mg^(2+),Al^(3+))batteries are considered as a prospective alternative for large-scale energy storage.However,the main problem of cathode materials for multivalent-ion batteries is the sluggish diffusion of multivalent ions.Many cathode materials will self-adjust under electrochemical conditions to achieve the optimal state for multivalent-ion storage.In this review,the significant role of electrochemical in situ structural reconstruction of cathode materials is suggested.The types,basic characteristics,and formation mechanisms of reconstructed phases have been systematically discussed and commented.The most important insight we pointed out is that the cathode materials with loose structures after in situ electrochemical activation are conducive to the reversible diffusion of multivalent ions.Moreover,several crucial issues of electrochemical activation and reconstruction were further analyzed and discussed.The challenges and future perspectives are presented in the final section.

Tandem Co–O dual sites on halloysite with promoted reaction kinetics for sulfur reduction

Facilitating sulfur reduction reaction(SRR)is a promising pathway to tackle the polysulfide shuttle effect and enhance the electrochemical performance of lithium-sulfur(Li-S)batteries.Catalysts with a solo active site can reduce a reaction barrier of a certain transition-intermediate,but the linear scaling relationship between multi-intermediates still obstructs overall SRR.Herein,we construct tandem Co–O dual sites with accelerating SRR kinetics by loading highly dispersed cobalt sulfide clusters on halloysite.This catalyst features Co with upshifted d-orbital and O with downshifted p-orbital,which cooperatively adsorb long-chain polysulfide and dissociate an S–S bond,thus achieving both optimal adsorption–desorption strength and reduced conversion energy barrier of multi-intermediates in SRR.The Li-S coin batteries using the electrocatalyst endows a high specific capacity of 1224.3 m Ah g^(-1)at 0.2 C after 200cycles,and enhances cycling stability with a low-capacity decay rate of 0.03%per cycle at 1 C after1000 cycles.Moreover,the strategy of the tandem Co–O dual sites is further verified in a practical Li-S pouch battery that realizes 1014.1 m Ah g^(-1)for 100 cycles,which opens up a novel avenue for designing electrocatalysts to accelerate multi-step reactions.

氧化硅基电解液用于稳定水系锌锰电池

由于水系电解液的活泼性,水系锌锰电池在低电流密度下稳定性仍然受到挑战。本文报道了一种新型实用的氧化硅基的ZnSO_(4)/MnSO_(4)混合溶液电解质(Si-ZMSO),显著提高了Zn-MnO_(2)电池体系的循环稳定性。Si-ZMSO电解液拓宽了电化学稳定窗口,同时能够抑制锌负极的副反应。因此,锌对称电池表现出了400 h以上的良好循环稳定性。与ZnSO4/MnSO4水系电解液(ZMSO)相比,使用这种新型的混合电解质还可以提高Zn-MnO2电池的循环稳定性能。电池在高负载量和低电流密度下循环200次后仍表现出良好的容量保持率。这种新颖的合成策略有望拓展水系锌锰电池的研究思路和发展。

Efficient anion immobilization enabled by structurally controllable halloysite for dendrite-free sodium metal anode

Sodium metal has shown great potential as an inexpensive anode for rechargeable batteries. However, the growth of sodium dendrites continues to hinder the commercialization of Na metal batteries. Herein, an effective strategy using anion-anchoring halloysite nanotube(HNT) coating was proven to prevent the diffusion of anions and trigger uniform Na deposition. Through theoretical calculation, a model of active site of fixed anions exposed from HNTs after acid activation was established for the first time, revealing that Si–Al sites are effective active site of acid-activated HNTs. Furthermore, HNTs with strong and effective adsorption capacity for anions were obtained by controlling the structure of HNTs to regulate the exposure of Si–Al sites. The strong interaction between sites of acid-activated HNTs and the SO_(3)CF_(3)^(-) anion effectively promotes the dissociation of sodium salts, the release of Na^(+) and subsequent migration. As a result, HNTs acid activation for 4 h shows a steady sodium deposition process and displays high Coulombic efficiency in half cell, long cycle life in symmetric cell and full cell. This work provides a basic theoretical basis for the design of nanoclay with abundant and effective active site to fix anions for dendritic free metal batteries.

Intercalated 2D nanoclay for emerging drug delivery in cancer therapy

Natural two-dimensional （2D） kaolinite nanoclay has been incorporated into an emerging drug delivery system. The basal spacing of the kaolinite nanoclay was expanded from 0.72 to 4.16 nm through the intercalation of various organic guest species of different chain lengths, which can increase the efficiency in drug delivery and reduce the toxicity of doxorubicin （DOX）. Original kaolinite （Kaolin） and the Kaolin intercalation compounds exhibited a high level of biocompatibility and very low toxicity towards cells of pancreatic cancer, gastric cancer, prostate cancer, breast cancer, colorectal cancer, esophageal cancer, and differentiated thyroid cancer. However, lung cancer and hepatocellular cancer cells need more strict compositional, structural, and morphological modulations for drug delivery carriers. DOX-Kaolin and the DOX-Kaolin intercalation compounds showed dramatically faster drug release in moderately acidic solution than in neutral condition, and exhibited enhanced therapeutic effects against ten model cancer cell cultures in a dose-dependent manner. The use of 2D nanoclay materials for a novel drug delivery system could feasibly pave a way towards high-performance nanotherapeutics, with superior antitumor efficacy and significantly reduced side effects.

Intercalated kaolinite as an emerging platform for cancer therapy

An innovative cancer therapy strategy regarding the interface engineering of kaolinite has been designed. The exposed silanol group facilitates more guest species with high dispersion on the supports. Mn_3O_4 magnetic nanoparticles are uniformly distributed on external surfaces of the Kaolin_(C12N)with the Al–O–Mn bond for the detection of the tumor microenvironment by T1-MRI; Doxorubicin(DOX) are loaded in the interlayer space with the electrostatic interaction for chemo-treating; and KI is coated on the outer layer of the nanocomposites based on the electrostatic interaction for thyroid cancer targeting. The synergetic effects and the treatment mechanism enhanced by the interface engineering, KI@DOX-Mn_3O_4-Kaolin_(C12N)can cause remarkably low cell viability(57%, 200 μg/mL), tumor shrinking(75%, 20 μg/kg), and accumulation into the tumor tissues. The novel kaolinite based drug delivery system is expected to incorporate imaging diagnosis, targeted therapy and drug delivery into one single system for postoperative residual thyroid cancer treatment and observation for metastasis of focal area.