Lithium‐rich layered oxides (LLOs) are prospective cathode materials for next‐generation lithium‐ion batteries (LIBs), but severe voltage decay and energy attenuation with cycling still hinder their practical applications. Herein, a series of full concentration gradient‐tailored agglomerated‐sphere LLOs are designed with linearly decreasing Mn and linearly increasing Ni and Co from the particle center to the surface. The gradient‐tailored LLOs exhibit noticeably reduced voltage decay, enhanced rate performance, improved cycle stability, and thermal stability. Without any material modifications or electrolyte optimizations, the gradient‐tailored LLO with medium‐slope shows the best electrochemical performance, with a very low average voltage decay of 0.8 mV per cycle as well as a capacity retention of 88.4% within 200 cycles at 200 mA g−1. These excellent findings are due to spinel structure suppression, electrochemical stress optimization, and Jahn‐Teller effect inhibition. Further investigation shows that the gradient‐tailored LLO reduces the thermal release percentage by as much as about 41% when the battery is charged to 4.4 V. This study provides an effective method to suppress the voltage decay of LLOs for further practical utilization in LIBs and also puts forward a bulk‐structure design strategy to prepare better electrode materials for different rechargeable batteries.

Magnetic flux leakage (MFL) sensors, with their compact configuration and high sensitivity to small defects, have attracted much attention in recent years for the non-destructive testing of ferromagnetic structures. Tunnel magneto-resistive (TMR) devices have superior performances in sensitivity and linear operation range over conventional magneto-resistive devices. In this paper, a commercial TMR device is employed for developing an electromagnet-based MFL sensor. The electromagnet magnetizer includes Helmholtz-like coils together with a custommade magnetic shield. The orthogonal test method is applied to aid the structural parameter optimization to the magnetizer based on the finite element analysis results of magnetic field distribution. In this study a prototype of a TMR-based MFL sensor is developed, and its performances on detecting various types of defects are tested on a scanning apparatus. The experimental results show that the MFL signal induced by a blind hole with dimensions of 0.3 mm in both depth and diameter is detectable. In addition, two adjacent notches located more than 2.0 mm from each other can be clearly distinguished from the received MFL signal. The detectable angular detection range for a single TMR device is estimated as 52°in the tested linear shaft rod. The consistency between the simulated and received MFL signal induced by a row of notches inspires confidence in the proposed sensor design method, which in the future can be transplanted for TMR-based sensor array design. Finally, the TMR-based MFL sensor is used for detecting a flaw of a single broken wire with a diameter of 0.5 mm, and the induced MFL signal can be clearly recognized from the oscillation signal that is generated by the twisted rope surface. Therefore, the presented TMR-based MFL sensor has great potential for steel wire rope inspection with enhanced sensitivity to small defects, and it is capable of being integrated into production lines due to its compact configuration.

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