Mathematical modeling and simulations of stress mitigation by coating polycrystalline particles in lithium-ion batteries

A chemo-mechanical model is developed to investigate the effects on the stress development of the coating of polycrystalline Ni-rich LiNixMnyCo_(z)O_(2)(x≥0.8)(NMC)particles with poly(3,4-ethylenedioxythiophene)(PEDOT).The simulation results show that the coating of primary NMC particles significantly reduces the stress generation by efficiently accommodating the volume change associated with the lithium diffusion,and the coating layer plays roles both as a cushion against the volume change and a channel for the lithium transport,promoting the lithium distribution across the secondary particles more homogeneously.Besides,the lower stiffness,higher ionic conductivity,and larger thickness of the coating layer improve the stress mitigation.This paper provides a mathematical framework for calculating the chemo-mechanical responses of anisotropic electrode materials and fundamental insights into how the coating of NMC active particles mitigates stress levels.

Amorphous Sb/C composite with isotropic expansion property as an ultra-stable and high-rate anode for lithium-ion batteries

Antimony(Sb)is an intriguing anode material for Li-ion batteries(LIBs)owing to its high theoretical capacity of 660 m Ah·g^(-1)and appropriate working potential of~0.8 V(vs.Li^(+)/Li).However,just like all alloying materials,the Sb anode suffers from huge volume expansion(230%)during repeated insertion/extraction of Li+ions,resulting in structural deterioration and rapid capacity decay.In this work,a novel amorphous Sb/C composite with atomically dispersed Sb particles in carbon matrix is prepared via a straightforward high-energy ball milling approach.The intimate intermixing of amorphous Sb with C provides homogeneous element distribution and isotropic volume expansion during cycling,resulting in persistent structural stability.Meanwhile,the disordered structure of amorphous material shortens the diffusion distance of lithium ions/electrons,promoting fast reaction kinetics and rate capability.Benefiting from the aforementioned effects,the amorphous Sb/C exhibits a high reversible capacity of537.4 m Ah·g^(-1)at 0.1 A·g^(-1)and retains 201.0 m Ah·g^(-1)at an ultrahigh current rate of 10.0 A·g^(-1).Even after 1500deep cycles at 2.0 A·g^(-1),the amorphous Sb/C electrode still maintains 86.3%of its initial capacity,which outperforms all existing Sb-based anodes reported so far.Postmortem analysis further reveals a greatly reduced volume variation of merely 34.6%for the amorphous Sb/C electrode,much lower than that of 223.1%for crystalline Sb materials.This study presents a new approach to stabilizing Sb-based alloy anodes and contributes to the construction of high-performance amorphous anode materials for LIBs,enabling advanced energy storage.

Carbon‐encapsulated anionic‐defective MnO/Ni open microcages: A hierarchical stress‐release engineering for superior lithium storage

Rational manipulation of multicomponent materials into a sophisticated architecture is a prerequisite for developing lithium‐ion batteries.However,mechanical diffusion‐induced strain accumulation leads to sluggish diffusion kinetics and anomalous structure instability,further resulting in inferior long‐term cyclability and rate performance.Herein,the von Mises stress distribution on open microcages composed of secondary nanoparticles(OCNs)is mechanically investigated by finite element simulation,which elucidates the pronounced stress‐release effect on OCNs architecture.Afterward,a facile metal–organic framework‐derived methodology is proposed for constructing multihierarchical carbon‐encapsulated oxygen vacancy‐enriched MnO/Ni OCNs(OV‐MnO/Ni OCNs).Due to structural and compositional integration,the OV‐MnO/Ni OCNs achieve extraordinary lithium storage performance with excellent reversible capacity(1905.1 mAh g^(−1) at 0.2 A g^(−1)),ultrahigh cycling stability(1653.5 mAh g^(−1) at 2 A g^(−1) up to 600 cycles),and considerable rate capability(463.3 mAh g^(−1) even at 10 A g^(−1)).The primary lithium storage mechanisms are further systematically determined by experimental and theoretical investigations.The enriched oxygen vacancies,metallic Ni configuration,and N‐doped carbonaceous matrix provide more active sites,construct omnidirectional diffusion pathways,suppress volume expansion,and boost electronic conductivity,thus yielding an exceptional diffusivity coefficient and expedited electrochemical kinetics.This study offers profound insights for the elaborate design of multicompositional electrodes into a mechanical stress‐release structure toward advanced energy storage application and development.

Challenges and strategies of lithium-rich layered oxides for Li-ion batteries

Lithium-ion batteries are considered a promising energy storage technology in portable electronics and electric vehicles due to their high energy density,competitive cost,and environmental friendliness.Improving cathode materials is an effective way to meet the demand for better batteries,of which the utilization of high-voltage cathode materials is an important development trend.In recent years,lithium-rich layered oxides have gained great attention due to their desirable energy density.This review presents the relationships between lattice structure and electrochemical properties,the underlying degradation mechanisms,and corresponding modification strategies.The recent progress and strategies are then highlighted,including element doping,surface coating,morphology design,size control,etc.Finally,a concise perspective for future developments and practical applications of lithium-rich layered oxides has been provided.

Selective lithium recovery from black powder of spent lithiumion batteries via sulfation reaction:phase conversion and impurities influence

The aim of this study is to present a new understanding for the selective lithium recovery from spent lithium-ion batteries(LIBs)via sulfation roasting.The composition of roasting products and reaction behavior of impurity elements were analyzed through thermodynamic calculations.Then,the effects of sulfuric acid dosage,roasting temperature,roasting time,and impurity elements were assessed on the leaching efficiency of valuable metals.Characterization methods such as X-ray diffraction(XRD),scanning electron microscopy-energy dispersive spectroscopy(SEM-EDS),and X-ray photoelectron spectroscopy(XPS)were employed to analyze the phase transformation mechanism during roasting process.The results indicate that after sulfation roasting(n(H_(2)SO_(4)):n(Li)=0.5,550℃,2 h),94%lithium can be selectively recovered by water leaching and more than 95%Ni,Co,and Mn can be leached through acid leaching without the addition of reduction agent.During the sulfation roasting process,the lithium in LiNi_(x)Mn_(y)Co_zO_(2)is mainly converted to Li_(2)SO_(4),while the Ni,Co and Mn are first transformed to sulfate and then converted into oxide form.In addition,impurity elements such as Al and F will combine with lithium to form LiF and LiAlO_(2),which will reduce the leaching rate of lithium.These results provide a new understanding on the mechanisms of phase conversion during sulfation roasting and reveal the influence of impurity elements for the lithium recovery from spent LIBs.

V-substituted pyrochlore-type polyantimonic acid for highly enhanced lithium-ion storage

Pyrochlore-structured polyantimonic acid(PAA)is a potential high-capacity electrode material,but its innately poor electroconductivity(~10^(-10)S/cm)seriously impairs its electrochemical reversibility for lithium-ion storage.Herein,we report design and synthesis of a novel V-substituted PAA(PAA-V),where V^(5+)are introduced to partially replace Sb^(5+).Owing to identical valence and close ionic radius relative to Sb^(5+),the V^(5+)cation can constitute the covalent VO_6octahedra framework without changing the pyrochlore crystal structure of PAA.As a result,the V^(5+)-substitution is capable to modulate the electronic structure of PAA with significantly improved electrical conductivity(~10^(-6)S/cm for PAA-V)and meanwhile decreases the size of crystals with reduced diffusion length for Li^(+)-ions.With varying the ratio of V^(5+)-substitution,the PAA-V with optimized substitution molar ratio(18%)exhibits the best lithium-ion storage performance,delivering a long cycling life with high reversible capacity(731 m Ah/g after 1200cycles at 1 A/g)and outstanding rate capability(279 mAh/g at 15 A/g).More importantly,by pairing the PAA-V as anode and commercial LiFePO_(4)as cathode,the full cell with a limited negative/positive capacity ratio of 1.2 exhibits decent cycling stability at 1 C after 150 cycles with 85.5%capacity retention.

构建具有应变缓冲结构的超细FeS/C复合材料用于持久储锂/钠

FeS因具有较高的比容量和优异的环境友好性,被认为是一种极具竞争力的锂/钠离子电池负极材料.然而,循环过程中缓慢的电荷转移动力学和较大的体积变化阻碍了它的实际应用.本文通过在超薄FeS/C复合材料中构建应变缓冲(气泡膜状)结构,从根本上解决了FeS动力学缓慢和体积变化大的问题.有限元模拟和非原位透射电镜结果验证了气泡膜状碳基质可作为保护壳层缓解FeS的巨大体积变化,还能提高其电子导电性.得益于这种独特的结构设计,该电极材料表现出显著增强的性能.其在5 A g^(-1)下的储锂容量为469 mA h g^(-1),在1 A g^(-1)下循环1500次后的储钠容量为354 mA h g^(-1).此外,由该电极与LiFePO_(4)正极组装的全电池即使在100次循环后也能提供558 mA h g^(-1)的比容量,展现出优异的循环稳定性.这一策略也可应用于其它导电性差、体积变化大的负极材料,以促进高倍率和长寿命电池的发展.