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1. Experimental Study of NCM-Si Batteries With Bi-Directional Actuation

   https://doi.org/10.1115/SMASIS2021-67596  

   Shan, Shuhua ; Gonzalez, Cody ; Rahn, Christopher ; Frecker, Mary ( September 2021 , 2021 ASME SMASIS)

   Silicon is regarded as one of the most promising anode materials for lithium-ion batteries. Its high theoretical capacity (4000 mAh/g) has the potential to meet the demands of high-energy density applications, such as electric air and ground vehicles. The volume expansion of Si during lithiation is over 300%, indicating its promise as a large strain electrochemical actuator. A Si-anode battery is multifunctional, storing electrical energy and actuating through volume change by lithium-ion insertion.

   To utilize the property of large volume expansion, we design, fabricate, and test two types of Si anode cantilevers with bi-directional actuation: (a) bimorph actuator and (b) insulated double unimorph actuator. A transparent battery chamber is fabricated, provided with NCM cathodes, and filled with electrolyte. The relationship between state of charge and electrode deformation is measured using current integration and high-resolution photogrammetry, respectively. The electrochemical performance, including voltage versus capacity and Coulombic efficiency versus cycle number, is measured for several charge/discharge cycles. Both configurations exhibit deflections in two directions and can store energy. In case (a), the largest deflection is roughly 35% of the cantilever length. Twisting and unexpected bending deflections are observed in this case, possibly due to back-side lithiation, non-uniform coating thickness, and uneven lithium distribution. In case (b), the single silicon active coating layer can deflect 12 passive layers.

    

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2. Silicon carbide (SiC) derived from agricultural waste potentially competitive with silicon anodes

   https://doi.org/10.1039/D2GC00645F  

   Yu, M. ; Temeche, E. ; Indris, S. ; Lai, W. ; Laine, R. M. ( April 2022 , Green chemistry)

   Biomass-derived materials offer low carbon approaches to energy storage. High surface area SiC w/wo 13 wt% hard carbon (SiC/HC, SiC/O), derived from carbothermal reduction of silica depleted rice hull ash (SDRHA), can function as Li+ battery anodes. Galvanostatic cycling of SiC/HC and SiC/O shows capacity increases eventually to >950 mA h g−1 (Li1.2–1.4SiC) and >740 mA h g−1 (Li1.1SiC), respectively, after 600 cycles. Post-mortem investigation via XRD and 29Si MAS NMR reveals partial phase transformation from 3C- to 6H-SiC, with no significant changes in unit cell size. SEMs show cycled electrodes maintain their integrity, implying almost no volume expansion on lithiation/delithiation, contrasting with >300% volume changes in Si anodes on lithiation. Significant void space is needed to compensate for these volume changes with Si in contrast to SiC anodes suggesting nearly competitive capacities. 6Li MAS NMR and XPS show no evidence of LixSi, with Li preferring all-C environments supported by computational modeling. Modeling also supports deviation from the 3C phase at high Li contents with minimal volume changes. 

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3. Synthesis and performance of nanostructured silicon/graphite composites with a thin carbon shell and engineered voids

   https://doi.org/10.1016/j.electacta.2017.10.198  

   Ashuri, M. ; He, Q. ; Liu, Y. ; Emani, S. ; Shaw, L. ( December 2017 , Electrochimica acta)

   Utilizing silicon as an anode material for Li-ion batteries has been the subject of many studies. However, due to the huge volume change of silicon during lithiation, the electrochemical performance of silicon is poor. Here, we have investigated a novel yet simple approach to synthesize nanostructured silicon/graphite composites with a carbon coating and engineered voids. High-energy ball mill is employed to convert micrometer-sized silicon and graphite to nanostructured silicon/graphite composite building blocks, while a thin carbon coating is applied to encapsulate these composite agglomerates, followed by partial etching of silicon to create engineered voids inside the composite agglomerates. The batteries made with this tailored nanostructure exhibit improved electrochemical performance over the counterparts made with silicon nanoparticles and exhibited a specific capacity of ~1800 mA h g-1 discharge capacity at the first cycle, 580 mA h g-1 after 40 cycles, and 350 mA h g-1 after 300 cycles. This study has established a novel method scalable at industry environment and capable of producing low cost Si anodes and clearly shown that the cycle stability of the tailored nanostructure improves with increasing engineered voids in the range we have investigated. 

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4. A Self‐Healing Room‐Temperature Liquid‐Metal Anode for Alkali‐Ion Batteries

   https://doi.org/10.1002/adfm.201804649  

   Guo, Xuelin ; Ding, Yu ; Xue, Leigang ; Zhang, Leyuan ; Zhang, Changkun ; Goodenough, John B. ; Yu, Guihua ( September 2018 , Advanced Functional Materials)

   Given the high energy density, alkali metals are preferred in rechargeable batteries as anodes, however, with significant limitations such as dendrite growth and volume expansion, leading to poor cycle life and safety concerns. Herein a room‐temperature liquid alloy system is proposed as a possible solution for its self‐recovery property. Full extraction of alkali metal ions from the ternary alloy brings it back to the binary liquid eutectic, and thus enables a self‐healing process of the cracked or pulverized structure during cycling. A half‐cell discharge specific capacity of up to 706.0 mAh g⁻¹in lithium‐ion battery and 222.3 mAh g⁻¹for sodium‐ion battery can be delivered at 0.1C; at a high rate of 5C, a sizable capacity of over 400 mAh g⁻¹for Li and 60 mAh g⁻¹for Na could be retained. Li and Na ion full cells with considerable stability are demonstrated when pairing liquid metal with typical cathode materials, LiFePO₄, and P2‐Na_2/3[Ni_1/3Mn_2/3]O₂. Remarkable cyclic durability, considerable theoretical capacity utilization, and reasonable rate stability present in this work allow this novel anode system to be a potential candidate for rechargeable alkali‐ion batteries.

    

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5. Zn(Cu)Si 2+ x P 3 Solid Solution Anodes for High‐Performance Li‐Ion Batteries with Tunable Working Potentials

   https://doi.org/10.1002/adfm.201903638  

   Li, Wenwu ; Liao, Jun ; Li, Xinwei ; Zhang, Lei ; Zhao, Bote ; Chen, Yu ; Zhou, Yucun ; Guo, Zaiping ; Liu, Meilin ( June 2019 , Advanced Functional Materials)

   Si‐based anodes with a stiff diamond structure usually suffer from sluggish lithiation/delithiation reaction due to low Li‐ion and electronic conductivity. Here, a novel ternary compound ZnSi₂P₃with a cation‐disordered sphalerite structure, prepared by a facile mechanochemical method, is reported, demonstrating faster Li‐ion and electron transport and greater tolerance to volume change during cycling than the existing Si‐based anodes. A composite electrode consisting of ZnSi₂P₃and carbon achieves a high initial Coulombic efficiency (92%) and excellent rate capability (950 mAh g⁻¹at 10 A g⁻¹) while maintaining superior cycling stability (1955 mAh g⁻¹after 500 cycles at 300 mA g⁻¹), surpassing the performance of most Si‐ and P‐based anodes ever reported. The remarkable electrochemical performance is attributed to the sphalerite structure that allows fast ion and electron transport and the reversible Li‐storage mechanism involving intercalation and conversion reactions. Moreover, the cation‐disordered sphalerite structure is flexible to ionic substitutions, allowing extension to a family of Zn(Cu)Si_2+xP₃solid solution anodes (x= 0, 2, 5, 10) with large capacity, high initial Coulombic efficiency, and tunable working potentials, representing attractive anode candidates for next‐generation, high‐performance, and low‐cost Li‐ion batteries.

    

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