Insights Into the Interfacial Degradation of High-Voltage All-Solid-State Lithium Batteries

Poly(ethylene oxide)(PEO)-based solid polymer electrolyte(SPE)is considered as a promising solid-state electrolyte for all-solid-state lithium batteries(ASSLBs).Nevertheless,the poor interfacial stability with high-voltage cathode materials(e.g.,LiCoO_(2))restricts its application in high energy density solid-state batteries.Herein,high-voltage stable Li_(3)AlF_(6) protective layer is coated on the surface of LiCoO_(2) particle to improve the performance and investigate the failure mechanism of PEO-based ASSLBs.The phase transition unveils that chemical redox reaction occurs between the highly reactive LiCoO_(2) surface and PEO-based SPE,resulting in structure collapse of LiCoO_(2),hence the poor cycle performance of PEO-based ASSLBs with LiCoO_(2) at charging voltage of 4.2 V vs Li/Li+.By sharp contrast,no obvious structure change can be found at the surface of Li_(3)AlF_(6)-coated LiCoO_(2),and the original layered phase was well retained.When the charging voltage reaches up to 4.5 V vs Li/Li+,the intensive electrochemical decomposition of PEO-based SPE occurs,leading to the constant increase of cell impedance and directly causing the poor performance.This work not only provides important supplement to the failure mechanism of PEO-based batter-ies with LiCoO_(2),but also presents a universal strategy to retain structure stability of cathode-electrolyte interface in high-voltage ASSLBs.

Thermal adaptation in overheated residential buildings in severe cold area in China

The winter in the severe cold area of China is long and cold. The mean outdoor temperature is about-10. 0 ℃ during the winter in Harbin,while the indoor air temperature is often above24 ℃. How does the indoor environment influence human thermal comfort and adaptation in such an overheated environment?A combined approach of spot-reading measurements and occupant interview s w as adopted in nine residential buildings of five communities during the heating period in 2013-2014. Tw enty residents w ere chosen as respondents. Totally 308 valid questionnaires w ere collected. The heating periods w ere separated into three phases based on the outdoor temperature.The results show that the mean indoor air temperatures in theearly-,mid-and late-heating periods w ere 23. 6 ℃,24. 3 ℃and 25. 0 ℃,respectively,w hich w ere larger than or close to the upper limit recommended by thermal comfort standards, and slightly higher than the related thermal neutral temperatures. With the heating process,the mean clothing insulation of residents decreased. Opening w indow s and reducing clothing w ere mainly taken by the residents to adapt to the overheated environment.The thermal neutral temperature has an upw ard tendency w ith the increasing indoor air temperature. On the other hand,overheating in residential buildings w ould make residents open w indow s,w hich may cause thermal discomfort and energy w aste. Therefore,the low er limit of the comfort indoor air temperature range should be suggested as the heating temperature,w hich could fully arouse residents' adaptation and achieve sustainable building designs.

Coil-to-Stretch Transition of Binder Chains Enabled by“Nano-Combs”to Facilitate Highly Stable SiO_(x) Anode

The commercialized binder carboxymethyl cellulose sodium(CMC-Na)is considered unsuitable for micro-sized SiO_(x) anode as it cannot endure the large volume change to retain the conductive network during repeated charge/discharge cycles.Herein,a small amount of silicon nanoparticles(SiNPs)is added during slurry preparation process as“nano-combs”to unfold the convoluted CMC-Na polymer chains so that they undergo a coilto-stretch transition by interaction between polar groups(e.g.,-OH,-COONa)of polymer and SiNPs’large surface.Through maximizing the utilization of binders,a uniform conductive network is constructed with increased interfacial contact with micro-sized SiO_(x).As a result,the SiO_(x) electrode with optimized(10 wt%)SiNPs addition shows significantly improved initial capacity and cycling performance.Through revisiting CMCNa,a currently deemed unqualified binder in SiO_(x) anode,this work gives a brand-new perspective on the failing mechanism of Si-based anode materials and an improving strategy for electrode preparation.

Regulating lithium affinity of hosts for reversible lithium metal batteries

Lithium(Li)metal batteries are regarded as the“holy grail”of nextgeneration rechargeable batteries,but the poor redox reversibility of Li anode hinders its practical applications.While extensive studies have been carried out to design lithiophilic substrates for facile Li plating,their effects on Li stripping are often neglected.In this study,by homogeneously loading indium(In)single atoms on N-doped graphene via In-N bonds,the affinity between Li and hosting substrates is regulated.In situ observation of Li deposition/stripping processes shows that compared with the N-doped graphene substrate,the introduction of In effectively promotes its reversibility of Li redox,achieving a dendrite-free Li anode with muchimproved coulombic efficiency.Interestingly,theoretical calculations demonstrate that In atoms have actually made the substrate less lithophilic via passivating the N sites to avoid the formation of irreversible Li-N bonding.Therefore,a“volcano curve”for reversible Li redox processes is proposed:the affinity of substrates toward Li should be optimized to a moderate value,where the balance for both Li plating and Li stripping processes could be reached.By demonstrating a crucial design principle for Li metal hosting substrates,our finding could trigger the rapid development of related research.

Influence of electrolyte structural evolution on battery applications:Cationic aggregation from dilute to high concentration

In the context of the rapid expansion of the electric vehicle market,the request for high-energy-density lithium-ion batteries(LIBs)has steadily increased,hence the demand for highly stable electrolytes.Over the past years,efforts have been devoted to the improvement of electrolyte materials.As a benchmarking breakthrough,the achievement of high concentration electrolyte(HCE)can be attributed to the altered cationic aggregation(i.e.,cation-solvent and cation-anion coordination environment),which offers technical superiority over the widely applied conventional dilute electrolytes.More recently,based on the understanding of the dilute electrolyte and HCE,the concept of localized HCE(LHCE)has been proposed and extensively investigated.All these findings reveal a roadmap of electrolyte optimization for high-performance LIBs via coordination structure regulation.Through elucidating the correlation of structure evolution therein and its critical effects on battery performance,this review aims to establish the design principle of electrolytes based on their structures other than component studies and thereby accelerate the development of high-performance electrolytes.