浓度梯度型LiNi_(1-2x)Co_xMn_xO_2材料的制备及性能研究

采用氨配合碳酸盐共沉淀法制备浓度梯度型N i1-2xCoxMnxCO3前驱体,通过固相法在不同煅烧温度下制备层状LiNi1-2xCoxMnxO2正极材料。通过扫描电镜、X射线衍射实验表明,该材料具有典型的α-NaFeO2层状结构,粒径在100~400 nm。经LAND电池测试系统在20℃,2.75~4.6V充放电电压范围内测试,在0.5、1、2、5 C倍率下,电池的首次放电比容量为174.1、168.8、147、108 mA.h/g,30次循环后放电比容量保持率分别为92%、87.5%、81.5%和62.3%,表现出较好的倍率特性。

梯度型LiNi_(1-2x)Co_xMn_xO_2材料的研究

采用碳酸盐共沉淀法制备了四层浓度梯度型Ni1-2xCoxMnxCO3前驱体,通过固相法在不同煅烧温度下制备层状LiNi1-2xCoxMnxO2正极材料。经扫描电镜、X射线衍射实验分析表明该材料具有α-NaFeO2层状结构,粒径在100～500nm。经LAND电池测试系统在20℃,2.75～4.5 V充放电电压范围内测试,充放电电流分别为0.5 C、1 C、2 C、5 C,电池的首次放电比容量为173.2、168.8、147和108 mAh/g,30次循环后放电比容量保持率分别为93%、87.5%、81.5%和62.3%。

电动工具用锂离子电池正极材料的研究进展

中国是世界上最重要的电动工具制造基地之一,也是主要的动力电池研发和生产国家。锂离子电池具有充放电倍率高、温度适应性宽、循环寿命长、无记忆效应、比功率/比能量高和性价比高等优点,正在全面取代Ni Cd、Ni H等传统电池,成为非插电式电动工具的新型动力。介绍了电动工具用锂离子电池的电化学性能和发展现状,比较了不同正极材料(三元NMC,磷酸铁锂LFP以及锰酸锂LMO等)对锂离子电池充放电性能的影响,讨论了电动工具用锂离子电池在不同温度下的倍率充放电、大功率和高倍率下的脉冲放电、快速充放电循环寿命、高温自放电稳定性以及电池在短路滥用条件下的安全性。

Effect of sintering temperature on cycling performance and rate performance of LiNi_(0.8)Co_(0.1)Mn_(0.1)O_2

LiNi0.8Co0.1Mn0.1O2 powder was prepared by mixing LiOH·H2O and co-precipitated Ni0.8Co0.1Mn0.1（OH）2 at a molar ratio of 1：1.05, followed by sintering at different temperatures. The effects of temperature on the morphology, structure and electrochemical performance were extensively studied. SEM and XRD results demonstrate that the sintering temperature has large influence on the morphology and structure and suitable temperature is very important to obtain spherical materials and suppresses the ionic distribution. The charge-discharge tests show that the electrochemical performance of LiNi0.8Co0.1Mn0.1O2 powders becomes better with the increase of temperature from 700 ℃ to 750 ℃ and higher temperature will deteriorate the performance. Although both of materials obtained at 750 ℃ and 780 ℃ demonstrate almost identical cyclic stability at 2C rate, which delivers 71.9%retention after 200 cycles, the rate performance of powder calcined at 780 ℃ is much poorer than that at 750 ℃. The XRD results demonstrate that the poor performance is ascribed to more severe ionic distribution caused by higher temperature.

Structure and electrochemical hydrogen storage characteristics of La_(0.8-x)Pr_xMg_(0.2)Ni_(3.15)Co_(0.2)Al_(0.1)Si_(0.05) (x=0-0.4) electrode alloys

For the purpose of improving the electrochemical cycle stability of the La-Mg-Ni based A2BT-type electrode alloys, both reducing Mg content and substituting La with Pr were adopted. The Lao.8-xPrxMg0.2Ni3.15Co0.2A10.1Si0.05 （x=0, 0.1, 0.2, 0.3, 0.4） electrode alloys were fabricated by casting and annealing. The investigation on the structures and electrochemical performances of the alloys was performed. The obtained results reveal that the as-cast and annealed alloys comprise two major phases, （La, Mg）2Ni7 phase with the hexagonal Ce2NiT-type structure and LaNi5 phase with the hexagonal CaCus-type structure, as well as a little residual LaNi3 phase. It is also found that the addition of Pr element observably affects the electrochemical hydrogen storage characteristics of the alloys, just as the discharge capacity and high rate discharge ability （HRD） first rise then fall with the growing of Pr content, and among all the alloys, the as-cast and annealed （x=0.3） alloys generate the largest discharge capacities of 360.8 and 386.5 mA.h/g, respectively. Additionally, the electrochemical cycle stability of all the alloys markedly grows with the increase of Pr content. The capacity retaining rate （S100） at the 100th charging and discharging cycle is enhanced from 64.98% to 77.55% for the as-cast alloy, and from 76.60% to 95.72% for the as-annealed alloy by rising Pr content from 0 to 0.4. Furthermore, the substitution of Pr for La results in first increase and then decrease in the hydrogen diffusion coefficient （D）, the limiting current density （IL） as well as the electrochemical impedance.

All-climate aqueous Na-ion batteries using “water-in-salt” electrolyte

Aqueous Na-ion batteries have been extensively studied for large-scale energy storage systems. However,their wide application is still limited by their inferior cycle stability(<3000 cycles) and poor temperature tolerance. Furthermore, many of the reported high rate behaviors are achieved at a low mass loading(<3 mg cm^(-2)) of the electrodes. Herein, we propose an aqueous Na-ion battery which includes a Ni-based Prussian blue(NiHCF) cathode, a carbonyl-based organic compound, 5,7,12,14-pentacenetetrone(PT)anode and a “water-in-salt” electrolyte(17 mol kg^(-1)NaClO_(4)in water). Its operation involves the reversible coordination reaction of the PT anode and the extraction/insertion of Na;in the NiHCF cathode. It is demonstrated that the wide internal spaces of the PT anode and NiHCF cathode can not only buffer the volumetric change induced by Na;storage, but also enable fast kinetics. The full cell exhibits a supercapacitor-like rate performance of 50 A g^(-1)(corresponding to a discharge or charge within 6.3 s)and a super-long lifespan of 15,000 cycles. Moreover, the excellent rate performance can still be preserved even with a high mass loading of the electrodes(15 mgNiHCFcm^(-2)and 8 mgPTcm^(-2)).Especially, the cell can work well in a wide temperature range, from-40 to 100 °C, showing a typical all-climate operation.

Mesoporous Fe_(3)O_(4)@C nanoarrays as high-performance anode for rechargeable Ni/Fe battery

Rechargeable aqueous batteries with high power density and energy density are highly desired for electrochemical energy storage.Despite the recent reports of various cathode materials with ultrahigh pseudocapacitance exceeding3000 F g^(-1)(or 800 mA h g^(-1)),the development of anode materials is relatively insufficient,which limits the whole performance of the devices far from practical applications.Herein,we report the preparation of mesoporous Fe_(3)O_(4)@C nanoarrays as high-performance anode for rechargeable Ni/Fe battery by a self-generated sacrificial template method.Zn O/Fe_(3)O_(4)composite was first synthesized by a co-deposition process,and Zn O was subsequently removed by alkali etching to construct the mesoporous structure.A thin carbon film was introduced onto the surface of the electrode by the carbonization of glucose to increase the structural stability of the electrode.The unique mesoporous nanoarray architecture endows the electrode with larger specific surface area,faster charge/mass transport and higher utilization of Fe_(3)O_(4),which shows an ultrahigh specific capacity (292.4 mA h g^(-1)at a current density of 5 mA cm^(-2)) and superior stability in aqueous electrolyte (capacitance retention of 90.8%after 5000cycles).After assembled with hierarchical mesoporous Ni O nanoarray as a cathode,an optimized rechargeable Ni/Fe battery with double mesoporous nanoarray electrodes was fabricated,which provided high energy/power densities(213.3 W h kg^(-1)at 0.658 kW kg^(-1)and 20.7 kW kg^(-1)at113.9 W h kg^(-1),based on the total mass of the active materials)in the potential window of 1.5 V with excellent cyclability(81.7%retention after 5000 charge/discharge cycles).

Hierarchical flower-like spinel manganese-based oxide nanosheets for high-performance lithium ion battery

Hierarchical flower-structured two-dimensional(2 D)nanosheet is favorable for electrochemical reactions.The unique structure not only exposes the maximized active sites and shortens ion/electron diffusion channels,but also inhibits the structural strain during cycling processes.Herein,we report the hierarchical flower-like pure spinel manganese-based oxide nanosheets synthesized via a template-orientated strategy.The oriented template is fabricated by decomposition of carbonate obtained from"bubble reaction",via an alcoholassisted hydrothermal process.The resultant spinel manganese-based oxide nanosheets simultaneously possess excellent rate capability and cycling stability.The high-voltage LiNi0.5Mn1.5O4(LNMO-HF)has a uniform phase distribution without the common impurity phase LixNi1-xO2 and NixO.Besides,the LNMO-HF delivers high discharge capacity of142.6 mA h g-with specific energy density of 660.7 W h kg 1 at 1 C under 55℃.More importantly,the template-orientated strategy can be extended to the synthesis of LiMn2 O4(LMO),which can achieve 88.12%capacity retention after 1000 cycles.

Defective 1T′-ReSe2 nanosheets vertically grown on elastic MXene for fast and stable potassium ion storage

The sluggish reaction kinetics and poor structure stability of transition metal dichalcogenides(TMDs)-based anodes in potassium-ion batteries(KIBs)usually cause limited rate performance and rapid capacity decay,which seriously impede their application.Herein,we report a vacancy engineering strategy for preparing a class of Te-doped 1T'-ReSe_(2)anchored onto MXene(Te-ReSe_(2)/MXene)as an advanced anode for KIBs with high performance.By taking advantage of the synergistic effects of the defective Te-ReSe_(2)arrays with expanded interlayers and the elastic MXene nanosheets with self-autoadjustable function,the Te-ReSe_(2)/MXene superstructure exhibits boosted K^(+)ion storage performance,in terms of high reversible capacity(361.1 mA h g^(−1)at 0.1 A g^(−1)over 200 cycles),excellent rate capability(179.3 mA h g^(−1)at 20 A g^(−1)),ultra-long cycle life(202.8 mA h g^(−1)at 5 A g^(−1)over 2000 cycles),and steady operation in flexible full battery,presenting one of the best performances among the TMDs-based anodes reported thus far.The kinetics analysis and theoretical calculations further indicate that satisfactory pseudocapacitive property,high electronic conductivity and outstanding K^(+)ion adsorption/diffusion capability corroborate the accelerated reaction kinetics.Especially,structural characterizations clearly elaborate that the Te-ReSe_(2)/MXene undergoes reversible evolutions of an initial insertion process followed by a conversion reaction.

Carbon-coating-increased working voltage and energy density towards an advanced Na3V2(PO4)2F3@C cathode in sodium-ion batteries

One main challenge for phosphate cathodes in sodium-ion batteries(SIBs)is to increase the working voltage and energy density to promote its practicability.Herein,an advanced Na3V2(PO4)2F3@C cathode is prepared successfully for sodium-ion full cells.It is revealed that,carbon coating can not only enhance the electronic conductivity and electrode kinetics of Na3V2(PO4)2F3@C and inhibit the growth of particles(i.e.,shorten the Na^+-migration path),but also unexpectedly for the first time adjust the dis-/charging plateaux at different voltage ranges to increase the mean voltage(from 3.59 to 3.71 V)and energy density from 336.0 to 428.5 Wh kg^-1 of phosphate cathode material.As a result,when used as cathode for SIBs,the prepared Na3V2(PO4)2F3@C delivers much improved electrochemical properties in terms of larger specifc capacity(115.9 vs.93.5 mAh g^-1),more outstanding high-rate capability(e.g.,87.3 vs.60.5 mAh g^-1 at 10 C),higher energy density,and better cycling performance,compared to pristine Na3V2(PO4)2F3.Reasons for the enhanced electrochemical properties include ionicity enhancement of lattice induced by carbon coating,improved electrode kinetics and electronic conductivity,and high stability of lattice,which is elucidated clearly through the contrastive characterization and electrochemical studies.Moreover,excellent energy-storage performance in sodium-ion full cells further demonstrate the extremely high possibility of Na3V2(PO4)2F3@C cathode for practical applications.

Achieving superior high-temperature sodium storage performance in a layered potassium vanadate

The high-temperature sodium-ion batteries(SIBs)used for large-scale energy storage have attracted extensive attention in recent years.However,the development of SIBs is still hampered mainly by their poor charge/discharge efficiency and stability,necessitating the search for appropriate electrodes.A simple potassium ion intercalation process is used herein to obtain the potassium vanadate(KV_(3)O_(8))nanobelts.When serving as the anode for SIBs at a high temperature(60℃),the KV_(3)O_(8) nanobelts display superior sodium storage performance with a high capacity of 414mA h g^(-1) at 0.1Ag^(-1),remarkable rate capability(220mAh g^(-1) at 20Ag^(-1)),and super-long cycle life(almost no capacity fading at 10Ag^(-1) over 1000 cycles).Moreover,the ex-situ X-ray powder diffraction reveals no structural changes throughout the whole charge/discharge process,which further confirms their outstanding stability,indicating KV_(3)O_(8) nanobelts are a promising candidate for high-temperature SIBs.