Omni-functional simultaneous interfacial treatment for enhancing stability and outgassing suppression of lithium-ion batteries

Ni-rich layered oxides in lithium-ion batteries have problems with gas generation and electrochemical performance reduction due to residual lithium's reaction on the surface with the electrolyte.To address this issue,in this study,the Acid solvent evaporation(AsE)method has been proposed as a potential method to remove residual lithium while promoting the formation of a new LiNO_(3)-derived coating layer on the cathode surface.The reduction of residual lithium using the ASE method and the construction of a LiNO_(3)-derived coating layer suppresses gas evolution caused by the side effects of the electrolyte,improves electrochemical performance,and improves thermal stability by facilitating the smooth movement of lithium ions.Furthermore,the structural stability and resistance change due to the LiNO_(3)-derived coating layer effects is guaranteed through cycling and DCIR of the pouch cell.As a result,compared to Pristine,the capacity retention of coin cells increased by 8%after 100 cycles,and pouch cells increased by 25%after 160 cycles.In addition,after cycling the pouch cell,CO_(2) gas has significantly reduced by about 30%compared to Pristine using gas chromatography.The ASE method effectively forms a robust LiNO_(3)-derived coating layer on the cathode active material,which helps minimize electrolyte reactivity,suppress ,CO_(2) emissions,enhance surface structure stability,improve thermal stability,and improveoverallbatteryperformance.

Novel polyimide binder for achieving high-rate capability and long-term cycling stability of LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2) cathode via constructing polar and micro-branched crosslinking network structure

LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(NCM811)material,as the promising cathode candidate for next-generation highenergy lithium-ion batteries,has gained considerable attention for extremely high theoretical capacity and low cost.Nevertheless,the intrinsic drawbacks of NCM811 such as unstable structure and inevitable interface side reaction result in severe capacity decay and thermal runaway.Herein,a novel polyimide(denoted as PI-Om DT)constructed with the highly polar and micro-branched crosslinking network is reported as a binder material for NCM811 cathode.The micro-branched crosslinking network is achieved by using 1,3,5-Tris(4-aminophenoxy)benzene(TAPOB)as a crosslinker via condensation reaction,which endows excellent mechanical properties and large free volume.Meanwhile,the massive polar carboxyl(-COOH)groups provide strong adhesion sites to active NCM811 particles.These functions of PIOm DT binder collaboratively benefit to forming the mechanically robust and homogeneous coating layer with rapid Li+diffusion on the surface of NCM811,significantly stabilizing the cathode structure,suppressing the detrimental interface side reaction and guaranteeing the shorter ion-diffusion and electron-transfer paths,consequently enhancing electrochemical performance.As compared to the NCM811 with PVDF binder,the NCM811 using PI-Om DT binder delivers a superior high-rate capacity(121.07 vs.145.38 m Ah g^(-1))at 5 C rate and maintains a higher capacity retention(80.38%vs.91.6%)after100 cycles at 2.5–4.3 V.Particularly,at the high-voltage conditions up to 4.5 and 4.7 V,the NCM811 with PI-Om DT binder still maintains the remarkable capacity retention of 88.86%and 72.5%after 100 cycles,respectively,paving the way for addressing the high-voltage operating stability of the NCM811 cathode.Moreover,the full-charged NCM811 cathode with PI-Om DT binder exhibits a significantly enhanced thermal stability,improving the safety performance of batteries.This work opens a new avenue for developing high-energy NCM811 based lithium-ion batteries with long cycle-life and superior safety performance using a novel and effective binder.

Experimental Study on Long Cycling Performance of NCM523 Lithium-Ion Batteries and Optimization of Charge-Discharge Strategy

With the increasing demand for clean renewable energy and electric cars,people have put forward higher requirement for the energy storage system.One of the most successful lithium-ion batteries with a cathode combination of lithium nickel manganese cobalt oxide(also called NCM lithium-ion battery),has been playing an increasingly important role.So far,numerous research has been done on the fabrication of cathode material with optimization of its composition,design,and assembly of the battery system in order to improve the energy storage performance.However,most of the previous studies were conducted based on relatively short cycling time of testing,with limited charge-discharge cycles of no more than 1000.Thus the conclusions were insufficient to be applied in the practical working condition.In this work,by using the developed NCM523 lithium-ion batteries,we have performed a series of ultra-long cycling tests on the individual cell and its module,with a comprehensive study on the relationship between the retained capacity after long cycling time and the depth of discharge(DOD),charge-discharge rate and operating temperature.Optimization of the charge-discharge strategies on a single cell and the whole module was also made to effectively improve the overall energy storage efficiency.This experimental study offers a guideline for the efficient use of similar types of lithium-ion batteries in the practical working condition.The developed batteries together with the optimized charge-discharge strategy proposed here are promising to meet the requirements for applications of stationary energy storage and electric cars.

Promoting Si-graphite composite anodes with SWCNT additives for half and NCM 811 full lithium ion batteries and assessment criteria from an industrial perspective

Single wall carbon nanotube(SWCNT)additives were formulated into(im-Si-graphite composite electrodes and tested in both half cells and full cells with high nickel cathodes.The critical role of small amount of SWCNT addition(0.2 wt%)was found for significantly improving delithiation capacity,first cycle coulombic efficiency(FCE),and capacity retention.Particularly,Si(10 wt%)-graphite electrode exhibits 560 mAh/g delithiation capacity and 92%FCE at 0.2 C during the first chargedischarge cycle,and 91%capacity retention after 50 cycles(0.5 C)in a half cell.Scanning electron microscope(SEM)was used to illustrate the electrode morphology,compositions and promoting function of the SWCNT additives.In addition,full cells assembled with high nickel-NCM811 cathodes and fim-Si-graphite composite anodes were evaluated for the consistence between half and full cell performance,and the consideration for potential commercial application.Finally,criteria to assess Si-containing anodes are proposed and discussed from an industrial perspective.

Recent progress on the modification of high nickel contentNCM:Coating,doping,and single crystallization

High nickel content layered cathodes,represented by NCM(LiNi_(x)Co_(y)Mn_(z)O_(2),x+y+z=1),are now widely employed in the market of electric vehicles,owing to their high energy density.With the gradual increase of nickel content and capacity,the issues on cycling life and safety become more serious.In this review,various strategies for improving the performance of high nickel NCM are summarized on the aspects of surface coating,ionic doping,and singlecrystal NCM.The coating strategy was separately described according to the physical property of coating species,including inert material coating,Li^(+)-conductor coating,electronic conductor coating,and mixed conductor coating.These coating species help to suppress the interfacial oxidation of electrolytes by NCM,improving the cycling life and safety.The elemental doping in the crystal lattice of NCM is then presented in the aspects of cation,anion,and mixed-ion doping,which are beneficial to stabilize the layered structure during charge–discharge and so promote the electrochemical performance.In quite recent years,the strategy of single-crystal NCM was demonstrated to be a promising pathway,owing to the dramatically reduced surface area and grain boundary.Finally,the remaining unsolved challenges and future strategies for further development of NCM cathode materials are outlined.

Phosphorus-silicon-integrated electrolyte additive boosts cycling performance and safety of high-voltage lithium-ion batteries

Safety and energy density are significant for lithium-ion batteries(LIBs),and the flammable organic elec-trolyte is one of the most critical causes of the safety problem of LIBs.Although LiNi0.8 Co 0.1 Mn 0.1 O 2(NCM811)cathode with high capacity can improve the energy density,the interface stability between NCM811 cathode and electrolytes needs to be improved.Herein,we report a multifunctional additive,diethyl(2-(triethoxysilyl)ethyl)phosphonate(DETSP),which can suppress the flammability of the elec-trolyte and enhance the cycling stability of NCM811 cathode with a capacity retention of 89.9%after 400 cycles at 1 C,while that of the blank electrolyte is merely 61.3%.In addition,DETSP is compati-ble well with the graphite anode without impairing the electrochemical performances.Significantly,the performance and safety of NCM811/graphite full cells are also improved.Experimental and theoretical re-sults demonstrate that DETSP can scavenge acidic byproducts and is beneficial to form a stable cathode-electrolyte interface(CEI).Accordingly,DETSP can potentially be an effective solution to ameliorating the safety of the commercial electrolyte and improving the stability of high-voltage cathodes.

Realizing simultaneously enhanced energy and power density fullcell construction using mixed hard carbon/Li_(4)Ti_(5)O_(12) electrode

Practical applications of lithium-ion batteries(LIBs)with both high energy and power density are urgently demanded,which require suitable charge/discharge platform,fast charge-transfer kinetics,as well as optimal solid electrolyte interphase(SEI)layer of electrode materials.In this work,a high-performance lithium-ion battery(LIB)full cell was assembled by using commercial LiNi_(0.33)Co_(0.33)Mn_(0.33)O_(2)(NCM111)as the positive electrode and mixed Li_(4)Ti_(5)O_(12)(LTO)/hard carbon(HC)as the negative electrode.It reveals that the component ratio between LTO and HC plays a critical role in manipulating the electric conductivity and the electro-reaction platform.The electrochemical test results show that when the content of HC is 10 wt%,the as-constructed full cell demonstrates the best electrochemical,with a maximum energy density of 149.2 Wh·kg^(-1) and a maximum power density of2195 W·kg^(-1) at 10 A·g^(-1)(30 C).This outperforms all the assembled systems within our work range and the state-ofthe-art literatures.The NCM//Li_(4)Ti_(5)O_(12)+10 wt%HC battery system also exhibits a good capacity retention after1000 cycles at the current density of 1 A·g^(-1).This work provides a new approach to enhance the full-cell performance by mixing electrode materials with different charge potentials and reaction kinetics.

Operando Observation of Structural Evolution and Kinetics of Li[Ni0.6Co0.2Mn0.2]O2 at Elevated Temperature

Li[Ni0.6Co0.2Mn0.2]O2(NCM622)is one of the best commercialized cathodes in the battery field.However,poor cyclability at relatively high temperature hinders its multiple usages.Here,operando tests were performed to investigate the phase transitions and electron/ion transfer process of lavered NCM622 at 25 and 55℃.The identified spinel structure resulting in the poor cyclability at 55℃ guides the commercialization of batteries at high temperature.