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The huge volume expansion in Sn-based alloy anode materials (up to 360%) leads to a dramatic mechanical stress and breaking of particles, resulting in the loss of conductivity and thereby capacity fading. To overcome this issue, SnO2@C nano- rattle composites based on < 10 nm SnO2 nanoparticles in and on porous amorphous carbon spheres were synthesized using a silica template and tin melting diffusion method. Such SnO2@C nano-rattle composite electrodes provided two electrochemical processes: a partially reversible process of the SnO2 reduction to metallic Sn at 0.8 V vs. Li+/Li and a reversible process of alloying/dealloying of LixSny at 0.5 V vs. Li+/Li. Good performance could be achieved by controlling the particle sizes of SnO2 and carbon, the pore size of carbon, and the distribution of SnO2 nanoparticles on the carbon shells. Finally, the areal capacity of SnO2@C prepared by the melt diffusion process was increased due to the higher loading of SnO2 nanoparticles into the hollow carbon spheres, as compared with Sn impregnation by a reducing agent.

Lithium ion batteries are typically based on one of three positive-electrode materials, namely layered oxides, olivine- and spinel-type materials. The structure of any of them is 'resistant' to electrochemical cycling, and thus, often requires modification/post- treatment to improve a certain property, for example, structural stability, ionic and/or electronic conductivity. This review provides an overview of different examples of coatings and surface modifications used for the positive-electrode materials as well as various characterization techniques often chosen to confirm/detect the introduced changes. It also assesses the electrochemical success of the surface-modified positive-electrode materials, thereby highlighting remaining challenges and pitfalls.

LiCoO₂ is one of the most used cathode materials in Li-ion batteries. Its conventional synthesis requires high temperature (>800 °C) and long heating time (>24 h) to obtain the micronscale rhombohedral layered high-temperature phase of LiCoO₂ (HT-LCO). Nanoscale HT-LCO is of interest to improve the battery performance as the lithium (Li⁺) ion pathway is expected to be shorter in nanoparticles as compared to micron sized ones. Since batteries typically get recycled, the exposure to nanoparticles during this process needs to be evaluated.

Cathodes in lithium ion batteries consist of an ionic conductor, an electronic conductor and a binder in order to make a composite that is both electronically and ionically conductive. The carbon coating on the cathode material plays a critical role for the electrochemical properties of lithium ion batteries due to the increased electronic conductivity. We explain the relationship between the electrochemical properties and the characteristics of composites prepared using the ball-milling process in this report. We investigated two types of carbonaceous materials (graphite and carbon black) in LiCoO₂ electrodes. These selected carbon materials have different characteristics and structure upon ball-milling with LiCoO₂. The composite prepared by ball-milling for 5 min leads to better mixing of carbon and LiCoO₂, an intimate contact of carbon on LiCoO₂, a higher lithium ion diffusion (DLi) than non ball-milled and longer ball-milled composites. On the other hand, a longer time of ball-milling (30 and 60 min) decreases the electronic and ionic conductivity due to an increase of disordered structure of carbon and a thick and dense carbon coating layer on LiCoO₂ particles, preventing the diffusion of lithium ions, respectively.

Conductive carbon coatings on cathode materials play a critical role in the electrochemical performance of lithium ion batteries due to the increased electronic conductivity and the protective effect of the organic electrolyte on the cathode material. The composite structure of a cathode depends on the physicochemical properties of the carbonaceous materials. We investigated several types of carbonaceous materials in LiCoO₂ electrodes. Platelet-shaped graphite provided superior cyclic voltammograms and specific capacities of the LiCoO₂ electrodes compared to nanosized spherical carbon black. The platelet-shaped graphite mixed homogeneously with LiCoO₂ and coated on LiCoO₂ particles in the form of a thin layer via the ball-milling method. However, the nano-carbon black is dense and aggregates during the ball-milling process. The thick coating of nano-carbon black on the LiCoO₂ particles, which were observed in backscattered electron images collected during the SEM measurements, made the penetration of the liquid electrolyte through this thick carbon layer difficult.

The huge volume expansion in Sn-based alloy anode materials (up to 360%) leads to a dramatic mechanical stress and breaking of particles, resulting in the loss of conductivity and thereby capacity fading. To overcome this issue, SnO2@C nano- rattle composites based on < 10 nm SnO2 nanoparticles in and on porous amorphous carbon spheres were synthesized using a silica template and tin melting diffusion method. Such SnO2@C nano-rattle composite electrodes provided two electrochemical processes: a partially reversible process of the SnO2 reduction to metallic Sn at 0.8 V vs. Li+/Li and a reversible process of alloying/dealloying of LixSny at 0.5 V vs. Li+/Li. Good performance could be achieved by controlling the particle sizes of SnO2 and carbon, the pore size of carbon, and the distribution of SnO2 nanoparticles on the carbon shells. Finally, the areal capacity of SnO2@C prepared by the melt diffusion process was increased due to the higher loading of SnO2 nanoparticles into the hollow carbon spheres, as compared with Sn impregnation by a reducing agent.

Natrium super ionic conductor (NASICON) materials providing attractive properties such as high ionic conductivity and good structural stability are considered as very promising materials for use as electrodes for lithium- and sodium-ion batteries. Herein, a new high-performance electrode material, Li0.5Ni0.5Ti1.5Fe0.5(PO4)3/C, was synthesized via the sol–gel method and was electrochemically tested as an anode for lithium ion batteries, providing enhanced electrochemical performance as a result of nickel substitution into the lithium site in the LiTi2(PO4)3 family of materials. The synthesized material showed good ionic conductivity, excellent structural stability, stable long-term cycling performance, and improved high rate cycling performance compared to LiTi2(PO4)3. The Li0.5Ni0.5Ti1.5Fe0.5(PO4)3/C electrode delivered reversible capacities of about 93 and 68% of its theoretical one at current rates of 0.1 C (6.42 mA·g–1) after 100 cycles and 5 C (320.93 mA·g–1) after 1000 cycles, respectively. Theoretically, three Li+ ions can be inserted into the vacancies of the Li0.5Ni0.5Ti1.5Fe0.5(PO4)3/C structure. However, when the electrode is discharged to 0.5 V, more than three Li+ ions are inserted into the NASICON structure, leading to its structural transformation, and thus to an irreversible electrochemical behavior after the first discharge process.

Ni0.5Ti2(PO4)3/C NASICON‐type phosphate is introduced as a new anode material for lithium‐ion batteries (LIBs). Ni0.5Ti2(PO4)3/C was synthesized through the sol–gel route and delivered some remarkable electrochemical performances. Specifically, the Ni0.5Ti2(PO4)3/C electrode demonstrates a high rate capability performance and delivers high reversible capacities ranging from 130 mAh g−1 to about 111 mAh g−1 at current rates ranging from 0.1 C to 5 C in the voltage window of 1.85–3 V (vs. Li+/Li). In the same voltage range, the material reaches an initial capacity of 105 mAh g−1 with a capacity retention of about 82 % after 1000 cycles at the high current rate of 10 C. The electrodes are also tested in the wider voltage range of 0.5–3 V (vs. Li+/Li) and show good reversibility and rate capability performance. Moreover, the Ni0.5Ti2(PO4)3/C electrodes enable fast Li+ diffusion (in the order of 10−13 cm2 s−1) compared with other NASICON‐type materials. As a result, a first discharge capacity of 480 mAh g−1 is reached.

Lithium ion batteries are typically based on one of three positive-electrode materials, namely layered oxides, olivine- and spinel-type materials. The structure of any of them is 'resistant' to electrochemical cycling, and thus, often requires modification/post- treatment to improve a certain property, for example, structural stability, ionic and/or electronic conductivity. This review provides an overview of different examples of coatings and surface modifications used for the positive-electrode materials as well as various characterization techniques often chosen to confirm/detect the introduced changes. It also assesses the electrochemical success of the surface-modified positive-electrode materials, thereby highlighting remaining challenges and pitfalls.

Results of an early-stage sustainability evaluation of two development strategies for new nanoscale cathode materials for Li-ion batteries are reported: (i) a new production pathway for an existing material (LiCoO2) and (ii) a new nanomaterial (LiMnPO4). Nano-LiCoO2 was synthesized by a single-source precursor route at a low temperature with a short reaction time, which results in a smaller grain size and, thereby, a better diffusivity for Li ions. Nano-LiMnPO4 was synthesized by a wet chemical method. The sustainability potential of these materials was then investigated (at the laboratory and pilot production scales). The results show that the environmental impact of nano-LiMnPO4 is lower than that of the other examined nanomaterial by several factors regardless of the indicator used for comparison. In contrast to commercial cathode materials, this new material shows, particularly on an energy and capacity basis, results of the same order of magnitude as those of lithium manganese oxide (LiMn2O4) and only slightly higher values than those for lithium iron phosphate (LiFePO4); values that are clearly lower than those for high-temperature LiCoO2.

LiCoO₂ is one of the most used cathode materials in Li-ion batteries. Its conventional synthesis requires high temperature (>800 °C) and long heating time (>24 h) to obtain the micronscale rhombohedral layered high-temperature phase of LiCoO₂ (HT-LCO). Nanoscale HT-LCO is of interest to improve the battery performance as the lithium (Li⁺) ion pathway is expected to be shorter in nanoparticles as compared to micron sized ones. Since batteries typically get recycled, the exposure to nanoparticles during this process needs to be evaluated.

5–10 nm thin rod shaped LiMnPO₄ nanoparticles are synthesized by an improved thermal decomposition method. The synthesis parameters such as the concentration of surfactants, reaction temperature and time, as well as the presence of a solvent play a critical role in the formation of spherical, thin or thick nanorods, and needle-shaped particles of LiMnPO₄. A washing procedure to efficiently eliminate the surfactants attached to the surface of LiMnPO₄ nanoparticles is presented, avoiding thermal treatment at high temperatures. A nanocomposite LiMnPO₄ electrode provides a discharge capacity of 165 mAh/g at 1/40 C and 66 mAh/g at 1 C with only 10 wt% of total carbon additive. The characteristics of as-synthesized and low amount of carbon coated LiMnPO₄ are described as well as their electrochemical properties.

Nanoparticles of LiMnPO₄ were fabricated in rod, elongated as well as cubic shapes. The 1D Li⁺ preferred diffusion direction for each shape was determined via electron diffraction spot patterns. The shape of nano-LiMnPO₄ varied the diffusion coefficient of Li⁺ because the Li⁺ diffusion direction and the path length were different. The particles with the shortest dimension along the b-axis provided the highest diffusion coefficient, resulting in the highest gravimetric capacity of 135, 100 and 60 mAh g⁻¹ at 0.05C, 1C and 10C, respectively. Using ball-milling, a higher loading of nano-LiMnPO₄ in the electrode was achieved, increasing the volumetric capacity to 263 mAh cm⁻³, which is ca. 3.5 times higher than the one obtained by hand-mixing of electrode materials. Thus, the electrochemical performance is governed by both the diffusion coefficient of Li⁺, which is dependent on the shape of LiMnPO₄ nanoparticles and the secondary composite structure.

Conductive carbon coatings on cathode materials play a critical role in the electrochemical performance of lithium ion batteries due to the increased electronic conductivity and the protective effect of the organic electrolyte on the cathode material. The composite structure of a cathode depends on the physicochemical properties of the carbonaceous materials. We investigated several types of carbonaceous materials in LiCoO₂ electrodes. Platelet-shaped graphite provided superior cyclic voltammograms and specific capacities of the LiCoO₂ electrodes compared to nanosized spherical carbon black. The platelet-shaped graphite mixed homogeneously with LiCoO₂ and coated on LiCoO₂ particles in the form of a thin layer via the ball-milling method. However, the nano-carbon black is dense and aggregates during the ball-milling process. The thick coating of nano-carbon black on the LiCoO₂ particles, which were observed in backscattered electron images collected during the SEM measurements, made the penetration of the liquid electrolyte through this thick carbon layer difficult.

Cathodes in lithium ion batteries consist of an ionic conductor, an electronic conductor and a binder in order to make a composite that is both electronically and ionically conductive. The carbon coating on the cathode material plays a critical role for the electrochemical properties of lithium ion batteries due to the increased electronic conductivity. We explain the relationship between the electrochemical properties and the characteristics of composites prepared using the ball-milling process in this report. We investigated two types of carbonaceous materials (graphite and carbon black) in LiCoO₂ electrodes. These selected carbon materials have different characteristics and structure upon ball-milling with LiCoO₂. The composite prepared by ball-milling for 5 min leads to better mixing of carbon and LiCoO₂, an intimate contact of carbon on LiCoO₂, a higher lithium ion diffusion (DLi) than non ball-milled and longer ball-milled composites. On the other hand, a longer time of ball-milling (30 and 60 min) decreases the electronic and ionic conductivity due to an increase of disordered structure of carbon and a thick and dense carbon coating layer on LiCoO₂ particles, preventing the diffusion of lithium ions, respectively.