Theoretical evaluation of high-energy lithium metal phosphate cathode materials in Li-ion batteries

Lithium metal phosphates (olivines) are emerging as long-lived, safe cathode materials in Li-ion batteries. Nano-LiFePO₄ already appears in high-power applications, and LiMnPO₄ development is underway. Current and emerging Fe- and Mn-based intercalants, however, are low-energy producers compared to Ni and Co compounds. LiNiPO₄, a high voltage olivine, has the potential for superior energy output (>10.7 Wh in 18650 batteries), compared with commercial Li(Co,Ni)O₂ derivatives (up to 9.9 Wh). Speculative Co and Ni olivine cathode materials charged to above 4.5 V will require significant advances in electrolyte compositions and nanotechnology before commercialization. The major drivers toward 5 V battery chemistries are the inherent abuse tolerance of phosphates and the economic benefit of LiNiPO₄: it can produce 34% greater energy per dollar of cell material cost than LiAl_0.05Co_0.15Ni_0.8O₂, today's “standard” cathode intercalant in Li-ion batteries.     

Effect of electrolytes on the structure and evolution of the solid electrolyte interphase (SEI) in Li-ion batteries: A molecular dynamics study

We have studied the formation and growth of solid-electrolyte interphase (SEI) for the case of ethylene carbonate (EC), dimethyl carbonate (DMC) and mixtures of these electrolytes using molecular dynamics simulations. We have considered SEI growth on both Li metal surfaces and using a simulation framework that allows us to vary the Li surface density on the anode surface. Using our simulations we have obtained the detailed structure and distribution of different constituents in the SEI as a function of the distance from the anode surfaces. We find that SEI films formed in the presence of EC are rich in Li₂CO₃ and Li₂O, while LiOCH₃ is the primary constituent of DMC films. We find that dilithium ethylene dicarbonate, LiEDC, is formed in the presence of EC at low Li surface densities, but it quickly decomposes to inorganic salts during subsequent growth in Li rich environments. The surface films formed in our simulations have a multilayer structure with regions rich in inorganic and organic salts located near the anode surface and the electrolyte interface, respectively, in agreement with depth profiling experiments. Our computed formation potentials 1.0 V vs. Li/Li⁺ is also in excellent accord with experimental measurements. We have also calculated the elastic stiffness of the SEI films; we find that they are significantly stiffer than Li metal, but are somewhat more compliant compared to the graphite anode.     

Characterisation of charge and discharge behaviour of lithium ion batteries with olivine based cathode active material

This paper gives insight to the physical processes taking part during the two-phase transition in lithium intercalation compounds. The behaviour of olivine based electrodes is in the special focus of this work. These electrodes exhibit phase juxtaposition within the electrode particles over a wide state of charge (SOC) range. Measurements were made to explore effects related to the formation of distinct phase sequences within the particles. Asymmetric charge characteristics, a load history dependency of the internal resistance and a voltage effect related to the disappearance of certain phase regions (the later on called vanishing phase effect) were identified. Moreover, these measurements give evidence to the existence of stable phase regions inside the electrode active material. An intuitive model is given to visualize the phase regions within spherical olivine particles. Therefore an analytical approach is developed in order to take the geometry of the particles, the ion permeability as well as the size distribution of the particles in consideration. According to the developed approach and the obtained measurement results, an enhanced cell equivalent electrical circuit is evaluated, considering phase shell development effects.     

Application of bis(fluorosulfonyl)imide-based ionic liquid electrolyte to silicon-nickel-carbon composite anode for lithium-ion batteries

An ionic liquid electrolyte containing bis(fluorosulfonyl)imide (FSI) anion without any solvent is applied to a silicon-nickel-carbon (Si-Ni-carbon) composite anode for rechargeable lithium (Li)-ion batteries. The FSI-based ionic liquid electrolyte successfully provides a stable, reversible capacity for the Si-Ni-carbon anode, which is comparable to the performance observed in a typical commercialized solvent-based electrolyte, while a common ionic liquid electrolyte containing bis(trifluoromethanesulfonyl)imide (TFSI) anion without FSI presents no reversible capacity to the anode at all. Ac impedance analysis reveals that the FSI-based electrolyte provides very low interfacial and charge-transfer resistances at the Si-based composite anode, even when compared to the corresponding resistances observed in a typical solvent-based electrolyte. Galvanostatic cycling of the Si-based composite anode in the FSI-based electrolyte with a charge limitation of 800 mAh g⁻¹ is stable and provides a discharge capacity of 790 mAh g⁻¹ at the 50th cycle, corresponding to a cycle efficiency of 98.8%.     

Cerium and zinc: Dual-doped LiMn2O4 spinels as cathode material for use in lithium rechargeable batteries

Pristine spinel lithium manganese oxide (LiMn₂O₄) and zinc- and cerium-doped lithium manganese oxide [LiZn_xCe_yMn_2−x−yO₄ (x = 0.01–0.10; y = 0.10–0.01)] are synthesized for the first time via the sol–gel route using p-amino benzoic acid as a chelating agent to obtain micron-sized particles and enhanced electrochemical performance. The sol–gel route offers shorter heating time, better homogeneity and control over stoichiometry. The resulting spinel product is characterized through various methods such as thermogravimetic and differential thermal analysis (TG/DTA), Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX) and electrochemical galvanostatic cycling studies. Charge–discharge studies of LiMn₂O₄ samples heated at 850 °C exhibit a discharge capacity of 122 mAh g⁻¹ and a corresponding 99% coulombic efficiency in the 1st cycle. The discharge capacity and cycling performance of LiZn_0.01Ce_0.01Mn_1.98O₄ is found to be superior (124 mAh g⁻¹), with a low capacity fade (0.1 mAh g⁻¹ cycle⁻¹) over the investigated 10 cycles.     

Simple annealing process for performance improvement of silicon anode based on polyvinylidene fluoride binder

An annealing method has been reported for silicon anode based on polyvinylidene fluoride (PVDF) binder. High initial coulombic efficiency of 75.6% and a stable reversible capacity of 715.6 mAh g⁻¹ for 50 cycles have been obtained after annealing process. Such improvements are attributed to the enhanced cohesive ability of PVDF and the compact morphology of the electrode reconstructed by annealing, which improves the electronic contacts of silicon particles and stabilizes the electrode structure effectively. It is demonstrated that such annealing method is very economic and effective for performance improvement of silicon anode.     

Influence of order in stepwise electroless deposition on anode properties of thick-film electrodes consisting of Si particles coated with Ni and Cu

Nickel and copper were coated on Si particles by a stepwise electroless deposition technique in which the coating orders of the metals were exchanged. Thick-film electrodes for Li-ion batteries were prepared by a gas-deposition method using the coated Si particles, and the anode performance of these electrodes was investigated. For (Cu, Ni)-coated Si particles obtained by primary Cu deposition and successive Ni deposition, Cu and Ni metal layers were individually deposited on the Si particles. In contrast, in case of (Ni, Cu)-coated Si particles prepared by primary Ni deposition, Cu layer stacked on Ni layer owing to a high catalytic activity of Ni, forming a thicker coated layer. The latter electrode exhibited notably improved performance with the discharge capacities over 1000 mAh g⁻¹ maintained until 400th cycle. The layer stack of Cu on Ni is probably effective for a release of a stress from the Si particles during charge-discharge reactions.     

储能锂离子电池关键材料研究进展

在现有商品化二次电池中,锂离子电池的比能量最高、循环性能最好,而且因其电极材料选择的多样性,作为储能电池具有广阔的应用前景。锂离子电池发展面临一些问题：比能量、比功率和循环寿命有待提升,安全性还没有可靠保证,制造成本过高,等等。针对这些问题,人们从电池材料选择、电池结构设计、电池制备装配与工艺、电池管理系统等方面探索解决方案。本文结合作者所在研究团队开展的工作,介绍锂离子电池关键材料（正极、负极和电解质）的研究进展。     

A rechargeable lithium-ion battery module for underwater use

Portable underwater electrical power is needed for many commercial, recreational and military applications. A battery system is currently not available to meet these needs, which was the aim of this project. Lithium-ion battery cells (Panasonic (CGR18650E)) were chosen, based on their high energy density and availability. To increase their voltage, 8 battery cells were connected in series (“sticks”) and protected by encapsulating them into a polycarbonate tube; and 6 sticks were housed inside a triangular aluminum case (module). Testing was performed to determine the consistency of individual cells, sticks and module and during discharge/charging cycles. The effect of ambient temperature (T_A) was determined by instrumenting them with thermocouples. In addition, voltage and current were measured and used to determine the heat generated within the battery cell and were compared to theory. From these data, a radial temperature profile was determined for two battery sticks in the battery module. Collapse pressure was determined and compared to theory. The Panasonic (CGR18650E) cells delivered 2291 mAh each over a wide range of T_A and discharge/charge rates. The theoretical and experimental data showed that the temperature within the battery sticks and modules did not rise above or below their operating temperature range (−20 and 60 °C), in agreement with the models. The tubes encapsulating the sticks withstood pressures down to 305 m of sea water (msw) which was predicted by modeling. The Panasonic (CGR18650E) cells, sticks and module demonstrated that they provided sufficient electrical power, reliably and safely to be used in the underwater environment (1800-2000 kPa, 305 msw) over a wide range T_A, including high power requirement systems like an active thermal protection system that keeps a diver comfortable in extreme temperature conditions. The concept developed here can be modified to meet specific power requirements by varying the number of cell in series to achieve the desired voltage, and the number of sticks in parallel to provide the current capacity required.     

Reviews of selected 100 recent papers for lithium batteries#br# （Oct. 1，2017 to Nov. 30，2017）

该文是一篇近两个月的锂电池文献评述,我们以“lithium”和“batter*”为关键词检索了Web of Science从2017年10月1日至2017年11月30日上线的锂电池研究论文,共3750篇,选择其中100篇加以评论。正极材料主要研究了层状结构材料和高压尖晶石材料充放电过程中的结构演变和表面修饰作用。高容量的硅、硅基负极材料研究侧重于纳米材料、复合材料及反应机理研究。金属锂负极的研究侧重于通过表面覆盖层的设计来提高其循环性能。固态电解质方面制备方法和离子输运机理是研究重点,电解液添加剂的研究目标是提高电池充电至高电压时的稳定性。锂空电池、锂硫电池侧重于改进电池的循环性能。理论模拟工作包括材料体相、界面结构和输运性质,除了以材料为主的研究之外,针对电池分析、理论模拟和电池模型的研究论文也有多篇。     

Reviews of selected 100 recent papers for lithium batteries （Aug. 1,2015 to Sept. 30,2015）

该文是一篇近两个月的锂电池文献评述,我们以“lithium”和“batter*”为关键词检索了Web of Science 从2015年8月1日至2015年9月30日上线的锂电池研究论文,共有2432篇,选择其中100篇加以评论。正极材料主要研究了富锂相材料、三元材料和尖晶石材料的掺杂和表面包覆及界面层改进对其循环寿命的影响。高容量的硅、锡基复合负极材料研究侧重于SEI界面层、复合材料、黏线剂及反应机理研究,电解液添加剂、固态电解质、锂空电池、锂硫电池的论文也有多篇。理论模拟工作包括电极材料体相和界面结构以及电解质的输运性质,除了以材料为主的研究之外,针对电池的状态估计、失效分析、热安全分析的研究论文也有多篇。     

Reviews of selected 100 recent papers for lithium batteries （April 1,2015 to May 31,2015）

该文是一篇近两个月的锂电池文献评述,我们以“lithium”和“batter*”为关键词检索了Web of Science从2015年4月1日至2015年5月31日上线的锂电池研究论文,共有1416篇,选择其中100篇加以评论。正极材料主要研究了富锂相材料、三元材料和尖晶石材料的结构演变及掺杂和表面包覆对其循环寿命的影响。高容量的硅基负极材料研究侧重于纳米材料、复合材料、黏结剂及反应机理研究,电解液添加剂、固态电解质、锂硫电池的论文也有多篇。理论模拟工作包括电极材料体相和界面结构以及电解质的输运性质,除了以材料为主的研究之外,电池模型和针对电池的失效分析、热安全分析的研究论文也有多篇。     

Reviews of selected recent important papers for lithium batteries(Dec. 1,2013 to Jan. 31,2014)

该文是一篇近两个月的锂电池文献评述,我们以"lithium"和"batter*"为关键词检索了Web of Science从2013年12月1日至2014年1月31日上线的锂电池研究论文,共有971篇,选择其中90篇加以评论.层状氧化物正极材料的研究主要包括包覆等表面层改性对材料充放电循环寿命的影响,也有对钴酸锂材料的深入研究,高电压的尖晶石结构LiNi_0.5M_1.5O₄材料主要研究了掺杂和合成方法改进的影响,磷酸铁锂和锰酸锂的研究集中在充放电过程中结构变化的细致分析方面.高容量的硅基负极材料一直是研究的热点,碳材料与锗,锡等复合负极材料,电解液添加剂,锂空电池,锂硫电池的论文也有多篇.理论模拟工作包括正极材料和硅的动力学过程研究和电解液添加剂作用机理,锂空电池电极过程等.除了这些以材料为主的研究之外,针对电池的原位分析,电池模型的研究论文大量出现.     

Reviews of selected 100 recent papers for lithium batteries （Oct. 1,2014 to Nov. 30,2014）

该文是一篇近两个月的锂电池文献评述,我们以“lithium”和“batter*”为关键词检索了Web of Science从2014年10月1日至2014年11月30日上线的锂电池研究论文,共有971篇,选择其中100篇加以评论。层状氧化物正极材料主要研究了NCA的热稳定性及表面包覆对材料循环寿命的影响,高电压的尖晶石结构LiNi_0.5M_1.5O₄材料主要研究了掺杂和表面包覆的作用。高容量的硅、锡基负极材料研究侧重于纳米材料、复合材料、黏结剂及电极制备和反应机理研究,电解液添加剂、固态电解质、锂空电池、锂硫电池的论文也有多篇。理论模拟工作包括SEI研究、材料中的锂扩散和材料与电池安全性关系的分析,除了这些以材料为主的研究之外,针对电池的原位分析、电池模型、电极制造技术的研究论文也有多篇。     

Reviews of selected recent papers for lithium batteries (Oct. 1,2013 to Nov. 30,2013)

该文是一篇近两个月的锂电池文献评述,我们以"lithium"和"batter*"为关键词检索了Web of Science从2013年10月1日至2013年11月30日上线的锂电池研究论文,共有628篇,因从上月起Web of Science不提供按文章上线时间的查询功能,本期搜索可能遗漏偏多,因此文章总篇数偏少,我们仅选择其中75篇加以评论.层状氧化物正极材料的研究包括充放电循环过程中的结构衍变以及表面改性研究,高电压尖晶石结构LiNi_0.5M_1.5O₄材料的研究偏重于掺杂和表面改性,尖晶石LiMn₂O₄的工作包括改变前驱体和优化合成条件的研究,聚阴离子正极材料的研究偏重于高电压材料,负极研究以硅基负极材料为主,还包括钛酸锂,硬碳材料和合金化负极等.电解质的研究包括聚合物固体电解质,无机固体电解质以及锂盐特性分析.锂空气电池研究论文有多篇,电池分析方面包括热模型,寿命模型和阻抗分析等.理论计算包括力学分析,扩散过程和界面分析等.