Building Better Batteries in the Solid State: A Review

Pseudo-ternary LiBH4·LiCl·P2S5 system as structurally disordered bulk electrolyte for all-solid-state lithium batteries

The properties of the mixed system LiBH₄-LiCl-P₂S₅ are studied with respect to all-solid-state batteries. The studied material undergoes an amorphization upon heating above 60 °C, accompanied with increased Li⁺ conductivity beneficial for battery electrolyte applications. The measured ionic conductivity is ∼10^-3 S cm^-1 at room temperature with an activation energy of 0.40(2) eV after amorphization. Structural analysis and characterization of the material suggest that BH₄ groups and PS₄ may belong to the same molecular structure, where Cl ions interplay to accommodate the structural unit. Thanks to its conductivity, ductility and electrochemical stability (up to 5 V, Au vs. Li⁺/Li), this new electrolyte is successfully tested in battery cells operated with a cathode material (layered TiS₂, theo. capacity 239 mA h g^-1) and Li anode resulting in 93% capacity retention (10 cycles) and notable cycling stability under the current density ∼12 mA g^-1 (0.05C-rate) at 50 °C. Further advanced characterisation by means of operando synchrotron X-ray diffraction in transmission mode contributes explicitly to a better understanding of the (de)lithiation processes of solid-state battery electrodes operated at moderate temperatures.

Integrated Approach Based on Dual Extended Kalman Filter and Multivariate Autoregressive Model for Predicting Battery Capacity Using Health Indicator and SOC/SOH

To enhance the efficiency of an energy storage system, it is important to predict and estimate the battery state, including the state of charge (SOC) and state of health (SOH). In general, the statistical approaches for predicting the battery state depend on historical data measured via experiments. The statistical methods based on experimental data may not be suitable for practical applications. After reviewing the various methodologies for predicting the battery capacity without measured data, it is found that a joint estimator that estimates the SOC and SOH is needed to compensate for the data shortage. Therefore, this study proposes an integrated model in which the dual extended Kalman filter (DEKF) and autoregressive (AR) model are combined for predicting the SOH via a statistical model in cases where the amount of measured data is insufficient. The DEKF is advantageous for estimating the battery state in real-time and the AR model performs better for predicting the battery state using previous data. Because the DEKF has limited performance for capacity estimation, the multivariate AR model is employed and a health indicator is used to enhance the performance of the prediction model. The results of the multivariate AR model are significantly better than those obtained using a single variable. The mean absolute percentage errors are 1.45% and 0.5183%, respectively.

A Simple Dual-Ion Doping Method for Stabilizing Li-Rich Materials and Suppressing Voltage Decay

A gentle method is used to treat the precursor to induce the doping of SO₄^2- and Ni²⁺. The doped SO₄^2- induces the formation of oxygen vacancies and defects, which are beneficial for inhibition of the loss of O^2-, stabilization of the structure, and amelioration of voltage decay, and the doped Ni²⁺ increases the degree of lithium nickel mixing and significantly increases the midvoltage. After modification, the specific discharge capacity reaches 305.20 mAh g^-1, with a Coulombic efficiency of 86.20% (the specific discharge capacity and Coulombic efficiency of the original material are only 276.50 mAh g^-1 and 77.30%, respectively). In addition, the cycle performance is also significantly improved, and the discharge midvoltage is dramatically increased from 2.74 to 3.00 V after 350 cycles at a large current density of 1C due to the dual-ion synergistic effect. In summary, these results show that the materials exhibit not only a more stable structure but also better electrochemical performance after modification.

Sustainable and Environmentally Friendly Na and Mg Aqueous Hybrid Batteries Using Na and K Birnessites

Sodium and magnesium batteries with intercalation electrodes are currently alternatives of great interest to lithium in stationary applications, such as distribution networks or renewable energies. Hydrated laminar oxides such as birnessites are an attractive cathode material for these batteries. Sodium and potassium birnessite samples have been synthesized by thermal and hydrothermal oxidation methods. Hybrid electrochemical cells have been built using potassium birnessite in aqueous sodium electrolyte, when starting in discharge and with a capacity slightly higher than 70 mA h g⁻¹. Hydrothermal synthesis generally shows slightly poorer electrochemical behavior than their thermal counterparts in both sodium and potassium batteries. The study on hybrid electrolytes has resulted in the successful galvanostatic cycling of both sodium birnessite and potassium birnessite in aqueous magnesium electrolyte, with maximum capacities of 85 and 50 mA h g⁻¹, respectively.

Application Progress of Polyaniline, Polypyrrole and Polythiophene in Lithium-Sulfur Batteries

With the urgent requirement for high-performance rechargeable Li-S batteries, besides various carbon materials and metal compounds, lots of conducting polymers have been developed and used as components in Li-S batteries. In this review, the synthesis of polyaniline (PANI), polypyrrole (PPy) and polythiophene (PTh) is introduced briefly. Then, the application progress of the three conducting polymers is summarized according to the function in Li-S batteries, including coating layers, conductive hosts, sulfur-containing compounds, separator modifier/functional interlayer, binder and current collector. Finally, according to the current problems of conducting polymers, some practical strategies and potential research directions are put forward. We expect that this review will provide novel design ideas to develop conducting polymer-containing high-performance Li-S batteries.

Developing high safety Li-metal anodes for future high-energy Li-metal batteries: strategies and perspectives

Developing high-safety Li-metal anodes (LMAs) are extremely important for the application of high-energy Li-metal batteries. The recently state-of-the-art technologies, strategies and perspectives for developing LMAs are comprehensively summarized in this review.