All-solid-state lithium batteries are considered as one of the most promising alternatives to traditional lithium-ion batteries because of their high safety and high energy density. In order to further improve the energy density of all-solid-state lithium batteries, sulfide electrodes with high theoretical capacities and solid electrolytes with high ionic conductivities have been widely explored and successfully demonstrated in all-solid-state lithium batteries. However, the interfacial resistance arising from poor interfacial compatibility and loose contact seriously hinders the electrochemical performances of all-solid-state lithium batteries. Fe3S4 ultrathin nanosheets with a thickness of 15 nm are synthesized by a facile polyvinyl alcohol-assisted precipitation method. In order to achieve intimate contact between sulfide electrodes and sulfide solid electrolytes, Fe3S4 nanosheets are in situ coated with Li7P3S11 and employed as cathode materials in Li/75% Li2S–24% P2S5–1% P2O5/Li10GeP2S12/Fe3S4@Li7P3S11 all-solid-state lithium batteries to investigate their electrochemical performances. Fe3S4@Li7P3S11 nanocomposite electrodes exhibit higher discharge capacity and better rate capability than pristine Fe3S4 nanosheets. After 200 cycles, the discharge capacity remained at a high value of 1001 mA h g−1 at a current density of 0.1 A g−1. The superior cycling stability could be ascribed to intimate contact and low charge transfer resistance at the interface between electrodes and solid electrolytes.

Two-dimensional Co9S8 nanosheets with a thickness of ∼10 nm and lateral size of several hundred nanometers are facilely synthesized through a polyvinyl alcohol (PVA)-assisted precipitation process in an aqueous solution. The process has low energy consumption and is easy to scale-up. Compared to the Co9S8 nanoparticles with a diameter of 40 nm prepared through the same process without PVA, the Co9S8 nanosheets, employed as anode materials in lithium-ion batteries, exhibited enhanced rate capability and cycling stability due to their unique two-dimensional nanostructures. When discharging/charging at 1.0 A g−1, the Co9S8 nanosheets can deliver a reversible capacity as high as 746.8 mA h g−1 after 300 cycles, which is much higher than that of Co9S8 nanoparticles (63.6 mA h g−1), making the Co9S8 nanosheets promising candidates for anode materials in high-energy and high-power lithium ion batteries.

•Fundamental lithium storage behavior of solid-state battery with NCA is investigated.•The relationship between electrochemical performances and structure is revealed.•Particle size, surface impurities and defects affect the interfacial resistance.•A ball-milling followed by post-annealing is demonstrated to improve performances.•The NCA in NCA/Li10GeP2S12/Li-In cell exhibits a discharge capacity of 146 mAh g−1.An insightful study on the fundamental lithium storage behavior of all-solid-state lithium battery with a structure of LiNi0.8Co0.15Al0.05O2 (NCA)/Li10GeP2S12/Li-In is carried out in this work. The relationship between electrochemical performances and particle size, surface impurities and defects of the NCA positive material is systematically investigated. It is found that a ball-milling technique can decrease the particle size and remove surface impurities of the NCA cathode while also give rise to surface defects which could be recovered by a post-annealing process. The results indicate that the interfacial resistance between the NCA and Li10GeP2S12 is obviously decreased during the ball-milling followed by a post-annealing. Consequently, the discharge capacity of NCA in the NCA/Li10GeP2S12/Li-In solid-state battery is significantly enhanced, which exhibits a discharge capacity of 146 mAh g−1 at 25 °C.

MoS2 nanoflowers consisting of nanosheets are synthesized by a one-step hydrothermal method. The interlayer distances of the MoS2 nanosheets, accompanied with the changes of crystallinity, defects, specific surface areas as well as the thickness of the MoS2 nanosheets, can be well controlled via simply altering hydrothermal reaction temperatures. The effect of interlayer distances on the lithium storage capability for lithium ion batteries is investigated. The results show that MoS2 synthesized under 200 °C with an interlayer distance of 0.65 nm exhibit the highest lithium storage capacity and the best rate capability, showing a high discharge capacity of 814.2 mA h g−1 at 100 mA g−1 after 50 cycles and as high as 652.2 mA h g−1 and 547.3 mA h g−1 at current densities of 1 A g−1 and 2 A g−1 at 25 °C, respectively. The excellent lithium storage properties of the resultant MoS2 nanoflowers are attributed to its controllable optimized interplanar distance with good crystallinity, appropriate surface area and defects as well as thickness of the nanosheets.

•The synthesized Li10GeP2S12 shows higher ionic conductivity than Li3.25Ge0.25P0.75S4.•All-solid-state lithium batteries containing NCA cathode and LGPS were demonstrated.•NCA/Li10GeP2S12/Li-In battery shows superior electrochemical performances.•Li10GeP2S12 exhibits low interfacial resistance with NCA cathode materials.The effect of solid electrolytes, i.e. Li10GeP2S12 and Li3.25Ge0.25P0.75S4, on the rate and low temperature performances of LiNi0.8Co0.15Al0.05O2 (NCA) cathode in all solid state lithium batteries is investigated. The ionic conductivities for the synthesized Li10GeP2S12 and Li3.25Ge0.25P0.75S4 at room temperature (RT) are 8.27 × 10− 3 and 2.03 × 10− 3 S cm− 1, respectively. These solid electrolytes are demonstrated as electrolytes for all solid state lithium batteries containing NCA cathode for the first time. The results show that Li10GeP2S12 based battery exhibits superior rate performance (72.3 mAh g− 1 at 1 C, RT), cycling stability (capacity retention of 87.1% after 30 cycles at 0.1 C, RT) and low temperature performance (79.2 mAh g− 1 at 0.1 C and − 10 °C), which can be ascribed to its higher ionic conductivity and lower interfacial resistance between Li10GeP2S12 and NCA cathode. It is indicated that all solid state lithium batteries with NCA cathode and Li10GeP2S12 solid electrolyte can realize its potential application in high power and low temperature conditions.

A graphene-based nanocomposite Cu2ZnSnS4/graphene (CZTS/graphene) is employed as a promising active material for all-solid-state lithium batteries for the first time. Meantime, lithium metal is used as an anode in order to maximize the energy density of the batteries with the sulfide electrolytes. The solid electrolyte bilayer, i.e. Li10GeP2S12 and 70% Li2S–29% P2S5–1% P2O5, is designed, where 70% Li2S–29% P2S5–1% P2O5 is used as the interface with lithium metal for the purpose of avoiding the reduction reaction with Li10GeP2S12. CZTS/graphene nanocomposites, with the CZTS nanoparticles uniformly anchored on the graphene nanosheets, are prepared by a simple hydrothermal reaction. The unique structure endows significantly reduced lithium ion diffusion lengths in CZTS nanoparticles as well as intimate contact between CZTS nanoparticles and sulfide electrolytes, leading to favorable lithium ionic and electronic conduction pathways. The results reveal that the CZTS/graphene-21 in all-solid-state lithium batteries shows the discharge capacity of 645.4 mA h g−1 after 50 cycles at 50 mA g−1, corresponding to a very high energy density of 346.2 W h kg−1. Even at high current densities of 100 and 1000 mA g−1, the CZTS/graphene-21 can still deliver the discharge specific capacities as high as 544.6 and 233.9 mA h g−1 after 100 and 300 cycles, respectively.A graphene-based Cu2ZnSnS4 nanocomposite is demonstrated as a promising active material for all-solid-state lithium batteries, which shows good interfacial compatibility with sulfide electrolyte, resulting excellent rate capability and cycling stability. Meanwhile, lithium metal anode is employed in order to maximize the energy density of the all-solid-state lithium batteries, showing a high energy density of 346.2 W h kg−1 at 50 mA g−1.Download high-res image (268KB)Download full-size image