Energy Density Lithium-ion Batteries Research Articles

Thickness dependence of high volumetric energy density lithium ion battery based on Sn–Zn eutectic alloy foil anode

Thickness dependence of high volumetric energy density lithium ion battery based on Sn–Zn eutectic alloy foil anode

Insight into thermal analysis kinetics of surface protected LiNi0.8Co0.15Al0.05O2 cathode for safe lithium-ion batteries

Surface modification of Ni-rich cathode families has gained the most market interests towards energy-dense lithium-ion batteries (LIBs) due to its ability to strengthen LIBs electrochemical performance. Beyond current understandings, our study of thermal analysis kinetics has first revealed the indispensable role of surface coating against thermal decomposition, which is determinative for LIBs safety and large-scale commercialization. Al2O3 surface protection engages to induce inorganic-rich solid electrolyte interface (SEI) against its decomposition. Furthermore, it limits the formation, propagation and expansion of nanopores and dislocations inside particles, thus restraining transformation-metal ion dissolutions and oxygen releasing, which are the main reason to the stepwise thermal runaway and particle pulverization. Combined with the Arrhenius equation and non-isothermal kinetic equation, the kinetic triplet and decomposition mechanisms are well-defined for the first time, inherently elucidating the reduced decomposition rate and better safety caused by Al2O3-coating. This study has provided kinetic fundamentals and new insights of surface coating towards stable Ni-rich cathode and safe LIBs.

Spinel LiNi0.5Mn1.5O4 shell enables Ni-rich layered oxide cathode with improved cycling stability and rate capability for high-energy lithium-ion batteries

Increasing the charging cut-off voltage is an effective strategy to achieve high energy density Ni-rich layered oxide cathode materials, however the dramatic deterioration of cycling lifespan and thermal stability still remain great challenges in large-scale practical applications. Herein, a rationally designed core-shell structure LiNi0.9Co0.1O2@LiNi0.5Mn1.5O4 composite composed of spinel structure Mn-rich LiNi0.5Mn1.5O4 shell and layered structure Ni-rich LiNi0.9Co0.1O2 core is proposed to enhance the structure stability and thermal stability under high-voltage application scenario. Compared to the pristine LiNi0.9Co0.1O2 cathode, the core-shell structure LiNi0.9Co0.1O2@LiNi0.5Mn1.5O4 composite with optimized LiNi0.5Mn1.5O4 shell exhibits high reversible specific capacity (195.5 mA h g − 1 at 0.5 C), remarkable cycling stability (86% capacity retention after 100 cycles) and superior rate capability (162.5 mA h g − 1 at 5.0 C) within 2.8 V-4.5 V. The comprehensively improved electrochemical performance is mainly attributed to the Mn-rich LiNi0.5Mn1.5O4 shell, which not only effectively prevents the phase transition and microstructural collapse, but also ameliorates the Li+ transport ability, high-voltage charging capability and thermal stability. Such novel core-shell structure LiNi0.9Co0.1O2@LiNi0.5Mn1.5O4 composite as promising cathode is highly expected to greatly promote the practical application of high energy density lithium-ion batteries.

Boosting Cyclability and Rate Capability of SiOx via Dopamine Polymerization-Assisted Hybrid Graphene Coating for Advanced Lithium-Ion Batteries.

SiOx suffers from the 200% volume change during cycling and low electronic conductivity, resulting in poor cyclability and rate capability as a lithium-ion battery anode. Herein, we demonstrate a dopamine polymerization-guided carbon coating for SiOx anodes (SiOx@PDA@GNH). SiOx@PDA@GNH delivers charge capacities of 1269 and 1140 mA h·g-1 at charge rates of 0.05 and 3 C, respectively, and a capacity retention of 79.60% after 150 cycles at 1 C. A full cell with LiNi0.8Co0.1Mn0.1O2 or cathode demonstrates a capacity retention of >80% after 100 cycles at the rate of 0.33 C with an area capacity over 3.2 mA h·cm-2. Suppressed crack and overgrowth of the SEI layer are the key contributions for the improved performance. These results enlighten a practical pathway for the designing and modifications of SiOx anodes for high energy density lithium-ion batteries.

Lithium-Rich O2-Type Li0.66[Li0.22Ru0.78]O2 Positive Electrode Material

Increasing the energy density of lithium-ion batteries is an important step towards flexible electricity supply, which can be achieved by developing large-capacity positive electrodes. Lithium-rich oxides have been a longstanding research target because of their large capacity involving extra oxygen-redox reactions. In this work, we report the synthesis, electrochemical properties, electronic structure, and structural evolution of O2-type lithium-rich layered oxide Li1.22‒x Ru0.78O2. A robust Ru‒O layered framework without Ru migration allows for unveiling the solid-state electrochemistry of O2-type lithium-rich layered oxides with possibility of a large yet stable extra capacity for oxygen-redox reaction. Using a combination of X-ray photoelectron spectroscopy, X-ray absorption/emission spectroscopy, and in situ/ex situ X-ray diffraction, we clarified that O2-Li1.22‒x Ru0.78O2 delivers a large capacity of 200 mAh g‒1 in association with Ru5+/Ru4+ and Ru4+/Ru3+ two-electron redox reactions under a solid-solution process, but with no contribution from the extra oxygen-redox reaction.

The new-type batteries with ultimate energy density

In recent years, many countries have made plans for the development of electric vehicles. In 2021, the EU announced a plan to completely stop the sale of fuel cars by 2035 and replace all fuel cars with pure electric vehicles, reducing the carbon emissions to 100%. This is the most radical emissions reduction plan in history, and it means that the era of pure electric cars has officially arrived. The limited energy density of lithium-ion batteries currently used in cars has hampered the development of electric vehicle mileage. To meet the demand for electric vehicles, the development and research of high energy density batteries are urgent. Based on a review of the current literature, this paper summarizes the development history, working principles, current challenges and solutions of the solid-state battery, lithium-air batteries and nuclear batteries. The current dilemma for solid-state batteries is the lack of a suitable solid electrolyte, which is needed to possess high ionic conductivity of above 10 (mS/cm) at room temperature and negligible electronic conductivity with a high ionic transference number wide electrochemical stability windows. Lithium-air batteries have low power density, battery energy attenuation, and high safety performance. The research and application of nuclear batteries are more difficult, including low energy conversion rate and health problem. The result provides some guidance to researchers initially involved in the high energy density battery industry.

One Stone for Multiple Birds: A Versatile Cross-Linked Poly(dimethyl siloxane) Binder Boosts Cycling Life and Rate Capability of an NCM 523 Cathode at 4.6 V.

Increasing working voltage is a promising way to increase the energy density of lithium-ion batteries. Cycling and rate performance deteriorated due to excessive electrolyte decomposition and uncontrolled formation of a cathode-electrolyte interface (CEI) layer at a high voltage. A new concept is proposed to construct a high-voltage-stable electrode-electrolyte interface. An elastomeric poly(dimethyl siloxane) (PDMS) binder is incorporated into the electrode to modify the LiNi0.5Co0.2Mn0.3O2 (NCM 523) particle surface via an in situ cross-linking reaction between hydroxy-terminated PDMS and methyl trimethoxy silane promoted by moisture at ambient conditions (MPDMS). Improved electrochemical performance is achieved with the MPDMS binder in terms of reversible capacity (201 vs 185 mAh·g-1 at 0.2C), capacity retention (80 vs 68%, after 300 cycles at 1C), and rate performance (55.6% increase at 5C), as demonstrated by the NCM 523||Li half-cell. The NCM 523||graphite full-cell also shows improved performance at 4.6 V (147 vs 128 mAh·g-1, 82 vs 76%, after 200 cycles at 1C). The mechanism studies indicate that MPDMS exerts multiple effects, including cathode surface passivation, solvation structure tuning, electrolyte uptake enhancement, and mechanical stress relief. This work provides an inspiring route to realize high-voltage application of lithium-ion battery technology.

Boosting high voltage cycling of LiCoO2 cathode via triisopropanolamine cyclic borate electrolyte additive

Energy density of lithium-ion batteries (LIBs) can be promoted by raising the charge cutoff voltage, which faces the challenges of accelerated structural and interfacial degradation. Introducing a functional electrolyte additive is considered as an effective approach by forming a robust and protective cathode electrolyte interphase (CEI). Herein, triisopropanolamine cyclic borate (TPCB) additive is probed for the first time as an electrolyte additive to significantly enhance the interfacial stability of LiCoO2 (LCO) cathode at high charge cutoff voltages (≥4.6 V). With optimized 0.5% TPCB in electrolyte, a thin (about 8 nm) and dense CEI layer, containing C–N, B–O/B–F species and less LiF, is generated to suppress the decomposition of electrolyte at high voltages and alleviate structure damage of LCO during long-term cycling. As a result, the LCO cathode in the TPCB-modified electrolyte displays remarkably enhanced capacity retention of 82.2% after 200 cycles at 1C at high charge cut-off 4.6 V, exceeding that of 63.2% in the Base electrolyte.

Promoting Mechanistic Understanding of Lithium Deposition and Solid‐Electrolyte Interphase (SEI) Formation Using Advanced Characterization and Simulation Methods: Recent Progress, Limitations, and Future Perspectives

AbstractIn recent years, due to its great promise in boosting the energy density of lithium batteries for future energy storage, research on the Li metal anode, as an alternative to the graphite anode in Li‐ion batteries, has gained significant momentum. However, the practical use of Li metal anodes has been plagued by unstable Li (re)deposition and poor cyclability. Although tremendous efforts have been devoted to the stabilization of Li metal anodes, the mechanisms of electrochemical (re‐)deposition/dissolution of Li and solid‐electrolyte‐interphase (SEI) formation remain elusive. This article highlights the recent mechanistic understandings and observations of Li deposition/dissolution and SEI formation achieved from advanced characterization techniques and simulation methods, and discusses major limitations and open questions in these processes. In particular, the authors provide their perspectives on advanced and emerging/potential methods for obtaining new insights into these questions. In addition, they give an outlook into cutting‐edge interdisciplinary research topics for Li metal anodes. It pushes beyond the current knowledge and is expected to accelerate development toward a more in‐depth and comprehensive understanding, in order to guide future research on Li metal anodes toward practical application.

TiO2(B) nanosheets modified Li4Ti5O12 microsphere anode for high-rate lithium-ion batteries

With the increasing applications of Lithium-ion batteries in heavy equipment and engineering machinery, the requirements of rate capability are continuously growing. The high-rate performance of Li4Ti5O12 (LTO) needs to be further improved. In this paper, we synthesized LTO microsphere-TiO2(B) nanosheets (LTO-TOB) composite by using a solvothermal method and subsequent calcination. LTO-TOB composite combines the merits of TiO2(B) and LTO, resulting in excellent high-rate capability (144.8, 139.3 and 124.4 mAh g−1 at 20 C, 30 C and 50 C) and superior cycling stability (98.9% capability retention after 500 cycles at 5 C). Its excellent electrochemical properties root in the large surface area, high grain-boundary density and pseudocapacitive effect of LTO-TOB. This work reveals that LTO-TOB composite can be a potential anode for high power and energy density lithium-ion batteries.

Dictating the interfacial stability of nickel-rich LiNi0.90Co0.05Mn0.05O2 via a diazacyclo electrolyte additive – 2-Fluoropyrazine

Nickel-rich (Ni-rich) cathode materials, LiNixCoyMnzO2 (NCM, x ≥ 0.9, x + y + z = 1) hold great promise for developing high energy density lithium ion batteries especially for vehicle electrification. However, the practical application of Ni-rich cathode materials is still suffered from fast structural and interfacial degradation, and the resulted capacity decay. In this study, a diazacyclo type electrolyte additive, 2-fluoropyrazine (2-FP), was explored for the first time to boost the interfacial stabilization of single crystal LiNi0.90Co0.05Mn0.05O2 (NCM90) cathode. The capacity retention of the NCM90 is evidently promoted from 72.3% to 82.1% after 200 cycles at 1C (180 mA g−1) when adding 0.2% 2-FP into the electrolyte. The improvement of the electrochemical performance is ascribed to the generation of a compact and homogeneous cathode electrolyte interphase (CEI) film through ring-opening electrochemical polymerization of 2-FP upon the NCM90 electrode particles. This enhanced CEI layer benefits the suppression of the decomposition of LiPF6 electrolyte and the dissolution of the transition metals (Co and Mn), thus preventing the detrimental side reactions between the NCM90 electrode and the electrolyte.

Design Strategies of Flame-Retardant Additives for Lithium Ion Electrolyte

Abstract As the energy density of lithium-ion batteries continues to increase, battery safety issues characterized by thermal runaway have become increasingly severe. Battery safety issues have severely restricted the large-scale application of power batteries. Among them, the flammable liquid organic electrolyte is one of the main reasons for the safety hazards of battery thermal runaway. This article reviews the flame-retardant mechanism and research progress of phosphorus-based flame-retardant additives, nitrogen-based flame-retardant additives, and halogen-based flame-retardant additives. The design strategies of conventional flame-retardant additives and intelligent flame-retardant additives in lithium-ion batteries are summarized. Finally, a development direction and research prospects of flame-retardant additives in lithium-ion battery electrolytes are prospected.

Systematic study and effective improvement of voltammetry for accurate electrochemical window measurement of solid electrolytes

The availability of solid electrolytes promisingly boosts the energy density of lithium-ion batteries (LIBs), yet the accurate voltammetry measurement of their electrochemical windows (EWs) poses a longstanding and critical concern. In this work, the mechanism of EW measurement of electrolytes is explained using the electrical double layer theory. The influence of crucial variables in voltammetry, including the scan mode, the working electrode, and the selection of two- or three-electrode test systems is investigated. Furthermore, the step voltammetry method is proposed and applied to EW testing of the inorganic solid electrolyte Li10GeP2S12 for the first time. Finally, suggestions for EW measurement of electrolytes are presented. The results of this work promote a comprehensive understanding and more accurate EW measurement of electrolytes, facilitating the selection of suitable solid electrolytes to match different cathodes, thus advancing the development of safer high-energy density LIBs.

A facile method to fabricate lightweight copper coated polyimide film current collectors for lithium-ion batteries

Large inactive component mass ratio and internal resistance are two critical challenges in further realizing high energy and power density lithium-ion batteries. Herein, lightweight copper coated polyimide (PI@Cu) current collectors with a high electrical conductivity (2.25 × 105 S cm−1) and low area density (1.99 mg cm−2) are fabricated via a facile electroless copper deposition method. Compared with the commercial Cu foil current collector, lithium titanate anodes equipped with PI@Cu current collectors decrease the inactive component mass ratio and improve the gravimetric capacity based on the whole mass of the electrode. Meanwhile, the rough surface morphology of deposited Cu layers reduces the electrode layer/current collector interfacial resistance, resulting in a lower internal resistance and better rate capability. PI@Cu composite films are promising alternatives to the traditional copper foil current collectors for high energy density and power density lithium-ion batteries.

Synergistic Effect of TMSPi and FEC in Regulating the Electrode/Electrolyte Interfaces in Nickel-Rich Lithium Metal Batteries.

Nickel-rich LiNi0.8Co0.1Mn0.1O2 (NCM811) with respect to Li metal can enhance the energy density of lithium batteries effectively. However, the unstable Li deposition, together with the dissolution and migration of transition metal (TM) ions toward the anode deteriorate the cycle performance of NCM811||Li battery, especially when commercial carbonate electrolyte is used. Herein, tris(trimethylsilyl)phosphite (TMSPi) and fluoroethylene carbonate (FEC) are used to construct a dual-additive electrolyte, by which both electrodes can be protected. It is found that TMSPi can be preferentially adsorbed on the cathode surface through its strong coordination with Ni4+, playing the role as a HF scavenger and suppressing TM ions dissolution, as well as mitigating the structural degradation of the cathode effectively. When it comes to the lithium anode, the presence of TMSPi may lead to side reactions with Li metal, accompanied by fast dendrite growth. The introduction of FEC could facilitate the formation of stable electrode/electrolyte interfaces on both sides. Particularly, reduce the direct contact between TMSPi and Li anode, thus ameliorate the incompatibility issue. Consequently, the NCM811||Li cell with dual-additive demonstrates excellent capacity retention of 81.2% after 500 cycles at 1 C rate. As a sharp contrast, it only retains 13.9% in the one with blank electrolyte. The findings of this work provide a new insight into enhancing the cycle performance of NCM811||Li system via the synergistic effect between additives.

Sulfone-based electrolytes for high energy density lithium-ion batteries

In this work, localized high concentration electrolytes (LHCEs) based on tetramethylene sulfone (TMS) were designed. Similar to LHCEs based on other solvents, TMS-based LHCEs can achieve excellent compatibility with high energy density lithium-ion batteries (LIBs) when combined with a proper additive. The unique solvation structure of LHCEs facilitates the synergetic decomposition of anion, solvent and additive in the solid electrolyte interphase (SEI) formation. Proper combinations of the three constituents of the solvation sheaths in LHCEs can promote the formation of highly effective SEI on graphite negative electrode. The absence of LiPF6 in LHCEs also suppresses the degradation of positive electrode materials in LIBs. The superior interphasial properties of LHCEs are the key to realizing the long lifespan of high energy density LIBs.

Amorphous fluorine glaze for crack-free nickel-rich layered cathode grains under electrochemical cycling

Nickel-rich layered cathode is a potential alternative material for high energy density lithium-ion batteries, but suffers fast capacity fading due to cathode grain cracking and surface collapse. Herein, a facile fluorine glaze is proposed to modify LiNi0.8Co0.15Mn0.05O2 grain surfaces. The metal fluoride glaze prevents cathode from grain cracking and surface collapsing effectively, and further promotes lithium-ion transport. The as-protected LiNi0.8Co0.15Mn0.05O2 shows a reversible capacity of 193 mAh g−1 under the voltage range of 2.8–4.3 V, which can retain almost 100% after 400 cycles and excellent rate performance of 125 mAh g−1 at 10C, much better than pristine cathode. Moreover, typical pouch cell, using fluorine glaze modified LiNi0.8Co0.15Mn0.05O2 cathode, also harvests robust cycling performance of 87 % capacity retention after 250 cycles. Our work provides a general and simple strategy for high performance nickel-rich cathode with superior structural and chemical robustness.

Numerical and experimental characterisation of high energy density 21700 lithium-ion battery fires

High energy density lithium-ion batteries (LIBs) are well suited for electrical vehicle applications to facilitate extended driving range. However, the associated fire hazards are of concern. Insight is required to aid the development of protective and mitigation measures. The present study is focused on 4.8 Ah 21700 cylindrical LiNixCoyMnzO (NMC) LIBs at 100% state of charge (SOC) with the aim to develop a viable predictive tool for simulating LIB fires, quantifying the heat release rate and temperature evolution during LIB thermal runaway (TR). To aid the model development and provide input parameters, thermal abuse tests were conducted in extended volume accelerating rate calorimetry (EV-ARC) and cone calorimetry. Some cells were instrumented with inserted temperature probe to facilitate in-situ measurements of both cell internal and surface temperatures. The mean peak values of the heat release rate, cell surface and internal temperatures were experimentally found to be 3.6 kW, 753 °C and 1080 °C, respectively. An analytical model has been developed to predict cell LIB internal pressure evolution following vent opening. The model uses the measured cell internal temperature and EV-ARC canister pressure as input data. Its predictions serve as boundary condition in the three-dimensional computational fluid dynamics (CFD) simulation of TR induced fire using opensource code OpenFOAM. The predicted transient heat release rate compare favourably with the measurements in the cone calorimetry tests. Predictions have also been conducted for an open cluster to assess the likelihood of TR propagation in the absence of cell side rupture. The present modelling approach can serve as a useful tool to assess the thermal and environment hazards of TR induced fires and aid design optimisation of mitigation measures in enclosed cell clusters/modules.

A lightweight and low-cost liquid-cooled thermal management solution for high energy density prismatic lithium-ion battery packs

• A F2-type liquid cooling system with M mode arrangement of cooling plates is recommended. • The F2-LCS fully meets the temperature requirements of batteries at a 1C charge-discharge rate. • From the perspective of results, the optimal inlet temperature is approximately 18.75℃. • The upper limits of flow rate of cooling water at different charge-discharge rates are studied. Upgrading the energy density of lithium-ion batteries is restricted by the thermal management technology of battery packs. In order to improve the battery energy density, this paper recommends an F2-type liquid cooling system with an M mode arrangement of cooling plates, which can fully adapt to 1C battery charge–discharge conditions. We provide a specific thermal management design for lithium-ion batteries for electric vehicles and energy storage power stations. In addition, the influence of the type of liquid cooling system, discharge rate, inlet temperature and flow rate are investigated, along with the effect of cooling plate arrangement on the temperature uniformity, maximum temperature, cooling efficiency factor and comprehensive heat transfer performance of cooling systems. The experimental results showed that the F2-type liquid cooling system has more advantages in cooling efficiency and comprehensive heat transfer performance than other liquid cooling systems. The best arrangement mode is M and the optimal inlet temperature is approximately 18.75 ℃. The upper limits of cooling water rate of flow at different charging and discharging rates are also determined. Cooling water rates of flow should be no less than 6 and 12 L/h when batteries are discharged at the rates of 1 and 2C, respectively.

Application of Terpolymer Encapsulated Flame-Retardant Separator in Ni-Rich and High-Voltage Lithium-Ion Batteries

Increasing the working voltage of a Ni-rich cathode is considered as the most effective way to enhance the energy density of lithium-ion batteries (LIBs). However, high energy density brings safety hazards in LIBs, resulting from the structural instability of the cathode material and the oxidative decomposition of carbonate electrolyte under high-voltage conditions. Directly adding the proper amount of flame retardant to the liquid electrolyte reduces the safety hazards, but causes rapid decay in electrochemical performance. To achieve a balance, flame retardant of triphenyl phosphate (TPP) is encapsulated by poly(butyl methacrylate-acrylonitrile-styrene) (P(BMA-AN-St)) terpolymer during the electrospinning process ascribed from different physical properties of surface energy and polarity. Compared with the self-extinguishing time (SET) of 89.5 s g−1 for commercial polyethylene (PE) separator, the SET value of PT11 separator (P(BMA-AN-St): TPP = 1:1 (w:w)) is sharply reduced to 23.0 s g−1, although both separators present the similar ionic conductivity of 0.8 × 10−3 S cm−1 at room temperature. Whether in half-cells of LiNi0.8Co0.15Al0.05O2/Separator/Li or full-cells of LiNi0.8Co0.15Al0.05O2/Separator/graphite, PE and PT11 separator show parallel cycle stability between 3.0 and 4.5 V. Thus, terpolymer encapsulated flame-retardant separator achieves both improved flame retardancy and competent electrochemical stability, making it become a good candidate for high-energy-density LIBs.