Zhiwei Li

Doping to control carrier (electron or hole) transport is foundational to modulate the properties of semiconductors, enabling the development of homojunctions and heterojunctions for integrated electronics. Unlike semiconductors with unipolar charge-carrier dominance, both cations and anions in electrolytes are mobile, which is undesirable for many applications. Here, we report a universal strategy to dope electrolytes such that the ion transport can be unipolar by incorporating electroactive polymers within hydrogels that interact discriminately with one type of ion via redox and binding mechanisms, leaving the counterions mobile. This transforms the system into an active, selective conductor that directs ion flow with high precision. We demonstrate the generality of this strategy using a wide range of electroactive polymers and ions. Particularly, we use emeraldine base and leucoemeraldine base, derived from polyaniline to create both n-type and p-type conductors with high ion selectivity. This electrolyte doping strategy has significant implications beyond the developed thermoelectrochemical devices with boosted performance, with potential applications in supercapacitors, batteries, and electrochemical sensors.

The development of safe and high‐performance polymer electrolytes is critical for advancing lithium metal batteries (LMBs). Herein, we report a PVDF‐HFP‐based polymer electrolyte incorporating two ionic liquids with different anions FSI ⁻ and TFSI ⁻ ‐to investigate their impact on structure and electrochemical behavior. The TFSI ⁻ ‐based system (PPIL) exhibits smaller particle size, reduced crystallinity, and enhanced amorphous β‐phase content, enabling improved ion mobility and a lower activation energy (69.0 kJ mol ⁻¹ ). Solid‐state NMR and Raman analyses reveal weaker Li ⁺ coordination in PPIL, consistent with its higher ionic conductivity (1.22 × 10 ⁻³ S cm ⁻¹ ). Interfacial characterizations show that PPIL promotes the formation of a stable, LiF/Li ₃ N‐rich SEI. As a result, LMBs using PPIL achieve over 2000 h of stable cycling, superior rate performance, and excellent thermal and mechanical safety in pouch cells. This work highlights the importance of ionic liquid anion design in optimizing polymer electrolytes for next‐generation energy storage systems.

A cascade photovoltaic platform transforms thermal management into simultaneous cooling and waste-heat electricity generation.

Ionic thermoelectric (i-TE) materials based on the thermodiffusion effect have shown great potential in low-grade heat conversion due to their exceptional heat-to-electricity properties, low cost, and flexibility. However, most current research has focused on p-type i-TE materials, leaving n-type i-TE materials underexplored by comparison. In addition, the current n-type i-TE materials still face some challenges such as unsatisfactory thermoelectric performance and the unclear mechanism of anion transport. Herein, we demonstrate an n-type i-TE hydrogel with hierarchical pathways for anion transport by employing an interpenetrating polymer network composed of sodium polystyrene sulfonate modified polyvinyl alcohol. Due to the coordination and electrostatic interactions between cations and functional groups, the hydrogel displays an n-type behavior with enhanced anion diffusion efficiency. The developed i-TE device not only shows excellent thermoelectric performance with a high thermopower of −16.8 ± 0.5 mV K⁻¹ and an output power density of 47.8 mW m⁻² at a temperature difference of 10 K, but also displays high sensitivity and responsivity to fluctuating heat input. This work provides valuable insights for the design and development of potential n-type i-TE materials and devices for low-grade heat conversion.

Thermodiffusion-based thermoelectrochemical cells have become one of the promising candidates for self-power supply by efficiently harvesting low-grade heat. However, fulfilling continuous energy output is still challenging because of the non-reciprocating motion of cations and anions during diffusion by adopting a steady heat source. Herein, we propose a moderate-concentration phase-change electrolyte for tuning the thermodiffusion process and the thermopower. Interestingly, the dominant ion can be alternated between cations and anions only by operando regulation of the physical state of the as-designed electrolyte, enabling the reversible polarization of devices from the p-type to the n-type with a tunable thermopower from 3.2 to −2.1 mV K⁻¹. Moreover, the correlation of phase transition behaviors, solvation structures, and thermoelectrochemical performances is investigated. As a proof-of-concept, a prototype module consisting of n-type and p-type units connected in series displays high sensitivity and stability for long-term power generation under light irradiation, demonstrating the potential of phase-change electrolytes in energy-related applications.

Flexible power supply devices provide possibilities for wearable electronics in the Internet of Things. However, unsatisfying capacity or lifetime of typical batteries or capacitors seriously limit their practical applications. Different from conventional heat-to-electricity generators, zinc ion thermal charging cells has been a competitive candidate for the self-power supply solution, but the lack of promising cathode materials has restricted the achievement of promising performances. Herein, we propose an attractive cathode material by rational heterostructure engineering of hydrated vanadium pentoxide. Owing to the integration of thermodiffusion and thermoextraction effects, the thermopower is significantly improved from 7.8 ± 2.6 mV K⁻¹ to 23.4 ± 1.5 mV K⁻¹. Moreover, an impressive normalized power density of 1.9 mW m⁻² K⁻² is achieved in the quasi-solid-state cells. In addition, a wearable power supply constructed by three units can drive the commercial health monitoring system by harvesting body heat. This work demonstrates the effectiveness of electrodes design for wearable thermoelectric applications.

Flexible power supply devices provide possibilities for wearable electronics in the Internet of Things. However, unsatisfying capacity or lifetime of typical batteries or capacitors seriously limit their practical applications. Different from conventional heat-to-electricity generators, zinc ion thermoelectrochemical cells has been a competitive candidate for the self-power supply solution, but the lack of promising cathode materials has restricted the achievement of promising performances. Herein, we propose an attractive cathode material by rational heterostructure engineering of hydrated vanadium pentoxide. Owing to the integration of thermodiffusion and thermoextraction effects, the thermopower is significantly improved from 9.1 mV K^− 1 to 25.3 mV K^− 1. Moreover, an impressive normalized power density of 2.7 mW m^− 2 K^− 2 is achieved in the quasi-solid-state cells. In addition, a wearable power supply constructed by three units can drive the commercial health monitoring system by harvesting body heat. This work demonstrates the effectiveness of electrodes design for wearable thermoelectric applications.