A sulfur‐rich copolymer@carbon nanotubes hybrid cathode is introduced for lithium–sulfur batteries produced by combining the physical and chemical confinement of polysulfides. The binderfree and ...metal‐current‐collector‐free cathode of dual confinement enables an efficient pathway for the fabrication of high‐performance sulfur copolymer carbon matrix electrodes for lithium–sulfur batteries.
Lithium–sulfur (Li–S) batteries are one of the most promising next‐generation batteries owing to their ultra‐high theoretical energy density and that sulfur is an abundant resource. During the past ...20 years, various sulfur materials have been reported. As a molecular‐scale sulfur‐composite cathode, sulfurized pyrolyzed poly(acrylonitrile) (S@pPAN) exhibits several competitive advantages in terms of its electrochemical behavior. Although it was first reported in 2002 S@pPAN is currently attracting increasing attention. In this Minireview, we summarize its molecular model and explore the correlation between its structure and its exceptional electrochemical performance. We classify the modification strategies into three types, including material improvement, binder, and electrolyte screening. Several research and development directions are also suggested.
Attention S@pPAN: As the representative of molecular scale sulfur composite cathode, sulfurized pyrolyzed poly(acrylonitrile) (S@pPAN) has attracted great attention owing to its superior electrochemical behavior. It avoids polysulfides dissolving and provides an alternative solid–solid conversion (SSC) process. Several research directions are proposed to build better batteries based on the promising S@pPAN composite.
Developing solid‐state electrolyte with sufficient ionic conduction and flexible‐intimate interface is vital to advance fast‐charging solid‐state lithium batteries. Solid polymer electrolyte yields ...the promise of interfacial compatibility, yet its critical bottleneck is how to simultaneously achieve high ionic conductivity and lithium‐ion transference number. Herein, single‐ion conducting network polymer electrolyte (SICNP) enabling fast charging is proposed to positively realize fast lithium‐ion locomotion with both high ionic conductivity of 1.1 × 10−3 S cm−1 and lithium‐ion transference number of 0.92 at room temperature. Experimental characterization and theoretical simulations demonstrate that the construction of polymer network structure for single‐ion conductor not only facilitates fast hopping of lithium ions for boosting ionic kinetics, but also enables a high dissociation level of the negative charge for lithium‐ion transference number close to unity. As a result, the solid‐state lithium batteries constructed by coupling SICNP with lithium anodes and various cathodes (e.g., LiFePO4, sulfur, and LiCoO2) display impressive high‐rate cycling performance (e.g., 95% capacity retention at 5 C for 1000 cycles in LiFePO4|SICNP|lithium cell) and fast‐charging capability (e.g., being charged within 6 min and discharged over than 180 min in LiCoO2|SICNP|lithium cell). Our study provides a prospective direction for solid‐state electrolyte that meets the lithium‐ion dynamics for practical fast‐charging solid‐state lithium batteries.
A network‐structured polymer electrolyte with simultaneous enhancement of ionic conductivity and lithium‐ion transference number is proposed as a positive strategy to boost fast ion transport and limit anion migration for kinetically propelling its lithium‐ion transport. These structural advantages with a synergistic effect obviously ameliorate the high‐rate cycling performance and fast‐charging capability of solid‐state lithium batteries.
A reaction‐protective separator that slows the growth of lithium dendrites penetrating into the separator is produced by sandwiching silica nanoparticles between two polymer separators. The reaction ...between lithium dendrites and silica nanoparticles consumes the dendrites and can extend the life of the battery by approximately five times.
Lithium metal is strongly regarded as a promising electrode material in next-generation rechargeable batteries due to its extremely high theoretical specific capacity and lowest reduction potential. ...However, the safety issue and short lifespan induced by uncontrolled dendrite growth have hindered the practical applications of lithium metal anodes. Hence, we propose a flexible anion-immobilized ceramic–polymer composite electrolyte to inhibit lithium dendrites and construct safe batteries. Anions in the composite electrolyte are tethered by a polymer matrix and ceramic fillers, inducing a uniform distribution of space charges and lithium ions that contributes to a dendrite-free lithium deposition. The dissociation of anions and lithium ions also helps to reduce the polymer crystallinity, rendering stable and fast transportation of lithium ions. Ceramic fillers in the electrolyte extend the electrochemically stable window to as wide as 5.5 V and provide a barrier to short circuiting for realizing safe batteries at elevated temperature. The anion-immobilized electrolyte can be applied in all–solid-state batteries and exhibits a small polarization of 15 mV. Cooperated with LiFePO₄ and LiNi0.5Co0.2Mn0.3O₂ cathodes, the all–solid-state lithium metal batteries render excellent specific capacities of above 150 mAh·g−1 and well withstand mechanical bending. These results reveal a promising opportunity for safe and flexible next-generation lithium metal batteries.
The lithium metal anode is regarded as a promising candidate in next‐generation energy storage devices. Lithium nitrate (LiNO3) is widely applied as an effective additive in ether electrolyte to ...increase the interfacial stability in batteries containing lithium metal anodes. However, because of its poor solubility LiNO3 is rarely utilized in the high‐voltage window provided by carbonate electrolyte. Dissolution of LiNO3 in carbonate electrolyte is realized through an effective solvation regulation strategy. LiNO3 can be directly dissolved in an ethylene carbonate/diethyl carbonate electrolyte mixture by adding trace amounts of copper fluoride as a dissolution promoter. LiNO3 protects the Li metal anode in a working high‐voltage Li metal battery. When a LiNi0.80Co0.15Al0.05O2 cathode is paired with a Li metal anode, an extraordinary capacity retention of 53 % is achieved after 300 cycles (13 % after 200 cycles for LiNO3‐free electrolyte) and a very high average Coulombic efficiency above 99.5 % is achieved at 0.5 C. The solvation chemistry of LiNO3‐containing carbonate electrolyte may sustain high‐voltage Li metal anodes operating in corrosive carbonate electrolytes.
Liquid assets: LiNO3 can be dissolved directly in an ethylene carbonate/diethyl carbonate electrolyte mixture by adding a trace amount of copper fluoride to promote dissolution. The solvation structure of the electrolyte system protects the lithium metal anode in a working high‐voltage lithium metal battery. NCA=LiNi0.80Co0.15Al0.05O2.
A gel polymer electrolyte (GPE) is a liquid electrolyte (LE) entrapped by a small amount of polymer network less than several wt%, which is characterized by properties between those of liquid and ...solid electrolytes in terms of the ionic conductivity and physical phase. Electrolyte leakage and flammability, demerits of liquid electrolytes, can be mitigated by using GPEs in electrochemical cells. However, the contact problems between GPEs and porous electrodes are challenging because it is difficult to incorporate GPEs into the pores and voids of electrodes. Herein, the focus is on GPEs that are gelated in situ within cells instead of covering comprehensive studies of GPEs. A mixture of LE and monomer or polymer in a liquid phase is introduced into a pre‐assembled cell without electrolyte, followed by thermal gelation based on physical gelation, monomer polymerization, or polymer cross‐linking. Therefore, GPEs are formed omnipresent in cells, covering the pores of electrode material particles, and even the pores of separators. As a result, different from ex situ formed GPEs, the in situ GPEs have no electrode/electrolyte contact problems. Functional GPEs are introduced as a more advanced form of GPEs, improving lithium‐ion transference number or capturing transition metals released from electrode materials.
Gel polymer electrolytes characterized by in situ gelation are presented. Different from ex situ gelated GPEs outside of electrochemical cells, in situ GPEs are formed omnipresent within cells covering the pores of the electrode material particles, and even the pores of the separators. The merits of in situ GPEs are demonstrated in electrochemical energy systems such as lithium‐ion batteries and lithium–sulfur batteries.
Lithium (Li) metal is a promising anode material for high‐energy density batteries. However, the unstable and static solid electrolyte interphase (SEI) can be destroyed by the dynamic Li ...plating/stripping behavior on the Li anode surface, leading to side reactions and Li dendrites growth. Herein, we design a smart Li polyacrylic acid (LiPAA) SEI layer high elasticity to address the dynamic Li plating/stripping processes by self‐adapting interface regulation, which is demonstrated by in situ AFM. With the high binding ability and excellent stability of the LiPAA polymer, the smart SEI can significantly reduce the side reactions and improve battery safety markedly. Stable cycling of 700 h is achieved in the LiPAA‐Li/LiPAA‐Li symmetrical cell. The innovative strategy of self‐adapting SEI design is broadly applicable, providing opportunities for use in Li metal anodes
Stretching exercises: A flexible lithium polyacrylic acid (LiPAA) solid electrolyte interphase (SEI) layer which is highly stretchable is designed to address the dynamic volume changes during Li plating/stripping on the Li anode surface in Li ion batteries. The LiPAA polymer SEI can significantly reduce the side reactions and improve the safety performance.
Water‐in‐salt (WIS) electrolytes using super‐concentrated organic lithium (Li) salts are of interest for aqueous Li‐ion batteries. However, the high salt cost, high viscosity, poor wettability, and ...environmental hazards remain a great challenge. Herein, we present a localized water‐in‐salt (LWIS) electrolyte based on low‐cost lithium nitrate (LiNO3) salt and 1,5‐pentanediol (PD) as inert diluent. The addition of PD maintains the solvation structure of the WIS electrolyte, improves the electrolyte stability via hydrogen‐bonding interactions with water and NO3− molecules, and reduces the total salt concentration. By in situ gelling the LWIS electrolyte with tetraethylene glycol diacrylate (TEGDA) monomer, the electrolyte stability window can be further expanded to 3.0 V. The as‐developed Mo6S8|LWIS gel electrolyte|LiMn2O4 (LMO) batteries delivered outstanding cycling performance with an average Coulombic efficiency of 98.53 % after 250 cycles at 1 C.
We present a localized water‐in‐salt gel electrolyte with low‐cost and high safety for aqueous lithium‐ion batteries. This electrolyte was fabricated by in situ gelling TEGDA monomer in an aqueous solution based on inexpensive LiNO3 salt and PD diluent. The as‐developed Mo6S8 | LWIS gel | LMO batteries delivered outstanding cycling performance with a Coulombic efficiency of 98.53 % % after 250 cycles at 1 C.
Due to high energy density, low cost, and nontoxicity, lithium–sulfur (Li–S) batteries are considered as the most promising candidate to satisfy the requirement from the accelerated development of ...electric vehicles. However, Li–S batteries are subjected to lithium polysulfides (LiPSs) shuttling due to their high dissolution in liquid electrolyte, resulting in low columbic efficiency and poor cycling performance. Moreover, the Li metal as an indispensable anode of Li–S batteries shows serious safety issues derived from the lithium dendrite formation. The replacement of liquid electrolytes with solid‐state electrolytes (SSEs) has been recognized as a fundamental approach to effectively address above problems. In this review, the progress on applying various classes of SSEs including gel, solid‐state polymer, ceramic, and composite electrolytes to solve the issues of Li–S batteries is summarized. The specific capacity of Li–S batteries is effectively improved due to the suppression of LiPSs shuttling by SSEs, while the rate and cycling performance remain relatively poor owing to the limited ionic conductivity and high interfacial resistance. Designing smart electrode/electrolyte integrated architectures, enabling the high ionic transportation pathway and compatible electrode/electrolyte interface, may be an effective way to achieve high performance solid‐state Li–S batteries.
This review aims to provide an overview of solid‐state electrolytes (gels, solid‐state polymers, ceramics, and composite electrolytes) for addressing the major drawbacks of Li–S batteries, including the lithium polysulfides shuttle effect and lithium dendrites initiation. In addition, strategies of overcoming deficiencies of solid‐state electrolytes such as low room‐temperature ionic conductivity and high interfacial resistance are also concluded.
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